up vote
22
down vote

favorite

Not to be confused with Least Common Multiple.

Given a list of positive integers with more than one element, return the most common product of two elements in the array.

For example, the MCM of the list [2,3,4,5,6] is 12, as a table of products is:

 2 3 4 5 6
 ---------------
2 | # 6 8 10 12
3 | # # 12 15 18
4 | # # # 20 24
5 | # # # # 30
6 | # # # # #

Thanks DJMcMayhem for the table

As 12 appears the most times (two times as 2*6 and 3*4). Note that we aren't including the product of an element and itself, so 2*2 or 4*4 do not not appear in this list. However, identical elements will still be multiplied, so the table for [2,3,3] looks like:

 2 3 3
 ----------
2 | # 6 6 
3 | # # 9
3 | # # #

With the MCM being 6.

In the event of a tie, you may return any of the tied elements, or a list of all of them.

This is code-golf, so the shortest byte count for each language wins!

Test-cases:

[2,3,4,5,6] -> 12
[7,2] -> 14
[2,3,3] -> 6
[3,3,3] -> 9
[1,1,1,1,2,2] -> 2
[6,200,10,120] -> 1200
[2,3,4,5,6,7,8,8] -> 24
[5,2,9,10,3,4,4,4,7] -> 20
[9,7,10,9,7,8,5,10,1] -> 63, 70, 90 or [63,70,90]

edited Aug 6 at 12:38

asked Aug 6 at 10:38

Jo King

14k13881

Sandbox (deleted)
â€“Â Jo King
Aug 6 at 10:39

4

Suggested test case: one where all elements are the same (i.e. [3,3,3] -> 9). With all your current test cases filtering out any pairs where elements are the same (even for test cases like [2,3,3] containing the same values) will still hold the correct test-results, but will fail for this test case because none will remain after filtering.
â€“Â Kevin Cruijssen
Aug 6 at 12:07

@Kevin Good suggestion, added
â€“Â Jo King
Aug 6 at 12:38

add a commentÂ |Â

up vote
22
down vote

favorite

Not to be confused with Least Common Multiple.

Given a list of positive integers with more than one element, return the most common product of two elements in the array.

For example, the MCM of the list [2,3,4,5,6] is 12, as a table of products is:

 2 3 4 5 6
 ---------------
2 | # 6 8 10 12
3 | # # 12 15 18
4 | # # # 20 24
5 | # # # # 30
6 | # # # # #

Thanks DJMcMayhem for the table

 2 3 3
 ----------
2 | # 6 6 
3 | # # 9
3 | # # #

With the MCM being 6.

In the event of a tie, you may return any of the tied elements, or a list of all of them.

This is code-golf, so the shortest byte count for each language wins!

Test-cases:

[2,3,4,5,6] -> 12
[7,2] -> 14
[2,3,3] -> 6
[3,3,3] -> 9
[1,1,1,1,2,2] -> 2
[6,200,10,120] -> 1200
[2,3,4,5,6,7,8,8] -> 24
[5,2,9,10,3,4,4,4,7] -> 20
[9,7,10,9,7,8,5,10,1] -> 63, 70, 90 or [63,70,90]

edited Aug 6 at 12:38

asked Aug 6 at 10:38

Jo King

14k13881

Sandbox (deleted)
â€“Â Jo King
Aug 6 at 10:39

4

Suggested test case: one where all elements are the same (i.e. [3,3,3] -> 9). With all your current test cases filtering out any pairs where elements are the same (even for test cases like [2,3,3] containing the same values) will still hold the correct test-results, but will fail for this test case because none will remain after filtering.
â€“Â Kevin Cruijssen
Aug 6 at 12:07

@Kevin Good suggestion, added
â€“Â Jo King
Aug 6 at 12:38

add a commentÂ |Â

up vote
22
down vote

favorite

Not to be confused with Least Common Multiple.

Given a list of positive integers with more than one element, return the most common product of two elements in the array.

For example, the MCM of the list [2,3,4,5,6] is 12, as a table of products is:

 2 3 4 5 6
 ---------------
2 | # 6 8 10 12
3 | # # 12 15 18
4 | # # # 20 24
5 | # # # # 30
6 | # # # # #

Thanks DJMcMayhem for the table

 2 3 3
 ----------
2 | # 6 6 
3 | # # 9
3 | # # #

With the MCM being 6.

In the event of a tie, you may return any of the tied elements, or a list of all of them.

This is code-golf, so the shortest byte count for each language wins!

Test-cases:

[2,3,4,5,6] -> 12
[7,2] -> 14
[2,3,3] -> 6
[3,3,3] -> 9
[1,1,1,1,2,2] -> 2
[6,200,10,120] -> 1200
[2,3,4,5,6,7,8,8] -> 24
[5,2,9,10,3,4,4,4,7] -> 20
[9,7,10,9,7,8,5,10,1] -> 63, 70, 90 or [63,70,90]

edited Aug 6 at 12:38

asked Aug 6 at 10:38

Jo King

14k13881

Not to be confused with Least Common Multiple.

Given a list of positive integers with more than one element, return the most common product of two elements in the array.

For example, the MCM of the list [2,3,4,5,6] is 12, as a table of products is:

 2 3 4 5 6
 ---------------
2 | # 6 8 10 12
3 | # # 12 15 18
4 | # # # 20 24
5 | # # # # 30
6 | # # # # #

Thanks DJMcMayhem for the table

 2 3 3
 ----------
2 | # 6 6 
3 | # # 9
3 | # # #

With the MCM being 6.

In the event of a tie, you may return any of the tied elements, or a list of all of them.

This is code-golf, so the shortest byte count for each language wins!

Test-cases:

[2,3,4,5,6] -> 12
[7,2] -> 14
[2,3,3] -> 6
[3,3,3] -> 9
[1,1,1,1,2,2] -> 2
[6,200,10,120] -> 1200
[2,3,4,5,6,7,8,8] -> 24
[5,2,9,10,3,4,4,4,7] -> 20
[9,7,10,9,7,8,5,10,1] -> 63, 70, 90 or [63,70,90]

edited Aug 6 at 12:38

asked Aug 6 at 10:38

Jo King

14k13881

edited Aug 6 at 12:38

asked Aug 6 at 10:38

Jo King

14k13881

asked Aug 6 at 10:38

Jo King

14k13881

asked Aug 6 at 10:38

Jo King

14k13881

Sandbox (deleted)
â€“Â Jo King
Aug 6 at 10:39

4

Suggested test case: one where all elements are the same (i.e. [3,3,3] -> 9). With all your current test cases filtering out any pairs where elements are the same (even for test cases like [2,3,3] containing the same values) will still hold the correct test-results, but will fail for this test case because none will remain after filtering.
â€“Â Kevin Cruijssen
Aug 6 at 12:07

@Kevin Good suggestion, added
â€“Â Jo King
Aug 6 at 12:38

add a commentÂ |Â

Sandbox (deleted)
â€“Â Jo King
Aug 6 at 10:39

4

Suggested test case: one where all elements are the same (i.e. [3,3,3] -> 9). With all your current test cases filtering out any pairs where elements are the same (even for test cases like [2,3,3] containing the same values) will still hold the correct test-results, but will fail for this test case because none will remain after filtering.
â€“Â Kevin Cruijssen
Aug 6 at 12:07

@Kevin Good suggestion, added
â€“Â Jo King
Aug 6 at 12:38

Sandbox (deleted)
â€“Â Jo King
Aug 6 at 10:39

Suggested test case: one where all elements are the same (i.e. [3,3,3] -> 9). With all your current test cases filtering out any pairs where elements are the same (even for test cases like [2,3,3] containing the same values) will still hold the correct test-results, but will fail for this test case because none will remain after filtering.
â€“Â Kevin Cruijssen
Aug 6 at 12:07

@Kevin Good suggestion, added
â€“Â Jo King
Aug 6 at 12:38

add a commentÂ |Â

22 Answers
22

active

oldest

votes

up vote
10
down vote

R, 54 50 41 bytes

order(-tabulate(combn(scan(),2,prod)))[1]

Try it online!

Alternatively, for 54 53 44 bytes:

names(sort(-table(combn(scan(),2,prod))))[1]

Try it online!

In principle, the latter version outputs the relevant result even without the names function, but followed by the count of such most frequent products, which isn't asked for...

Thanks to CriminallyVulgar for -4 and -1, and Giuseppe for -9 on both.

edited Aug 6 at 13:29

answered Aug 6 at 12:50

Kirill L.

2,0961114

1

On the second on you can use -table() instead of descending=TRUE for -1. I really like the cleverness of the first one though. EDIT: Just realised you can also apply that to the first one for -4, so there's that. Try it online!
â€“Â CriminallyVulgar
Aug 6 at 12:59

1

combn(scan(),2,prod) works instead of using apply
â€“Â Giuseppe
Aug 6 at 13:24

add a commentÂ |Â

up vote
8
down vote

Brachylog, 11 bytes

Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ—Ã¡Â¶Â Ã¡Â»ÂtÃ¡ÂµÂ’th

Try it online!

Explanation

 Ã¡Â¶Â  Find all:
 Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ— Product of a subset of 2 elements
 Ã¡Â»ÂtÃ¡ÂµÂ’ Order by occurrences
 th Take the last element and discard the number of occurrences

answered Aug 6 at 11:23

Fatalize

26.5k448133

I don't know how code golf usually works but aren't some of these characters outside the standard 256 code points and therefore multiple bytes each?
â€“Â Holloway
Aug 7 at 12:02

2

@Holloway Brachylog uses a custom code page
â€“Â Fatalize
Aug 7 at 12:07

add a commentÂ |Â

up vote
6
down vote

Pyth, 12 bytes

eo/QN=*M.cQ2

Test suite

First, we take all 2 element combinations of the input without replacement (.cQ2). Then, we map each of these pairs to their product (*M). Next, we overwrite the input variable with the list of products (=). Next, we sort the list of products by the number of occurrences in the list of products (o/QN). Finally, the take the final element of the sorted list (e).

answered Aug 6 at 10:51

isaacg

34.4k553185

add a commentÂ |Â

up vote
6
down vote

MATL, 8 7 bytes

2XN!pXM

Try it online!

(-1 byte by using the method from @Mr. Xcoder's Jelly answer.)

2XN % nchoosek - get all combinations of 2 elements from input
!p % get the product of each combination
XM % 'mode': get the most common value from that

Older answer:

8 bytes

&*XRXzXM

Try it online!

&* % multiply input by its transpose,
 % getting all elementwise products
XR % take the upper-triangular portion of that,
 % zeroing out repetitions and mainly self-multiplications
Xz % remove the zeroed out parts
XM % 'mode' calculation - get the most common value from that

edited Aug 6 at 13:37

answered Aug 6 at 13:27

sundar

4,383828

add a commentÂ |Â

up vote
6
down vote

Mathematica, 32 bytes

^{-17 bytes (and a fix) thanks to JungHwan Min.}

Commonest[1##&@@@#~Subsets~2]&

Pure function. Takes a list of numbers as input and returns the list of MCMs as output.

edited Aug 7 at 1:29

answered Aug 6 at 10:53

LegionMammal978

14.7k41752

Actually it looks like both of us misread the question. This fails for input 3, 3, 3. Fixed: Commonest[1##&@@@#~Subsets~2]&
â€“Â JungHwan Min
Aug 6 at 20:21

@JungHwanMin Huh. I thought that Subsets didn't count repeats as separate elements. It seems like it does, though, so thanks!
â€“Â LegionMammal978
Aug 7 at 1:28

add a commentÂ |Â

up vote
5
down vote

Jelly, 6 bytes

Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ

Try it online! or Check out the test suite.

How it works


Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Full program / Monadic link.
Ã…Â’c Ã¢Â€Â“ Unordered pairs without replacement.
 PÃ¢Â‚Â¬ Ã¢Â€Â“ Product of each.
 ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Mode (most common element).

Alternative: Ã…Â’cZPÃƒÂ†Ã¡Â¹Âƒ

edited Aug 6 at 11:18

answered Aug 6 at 11:10

Mr. Xcoder

29.4k756192

add a commentÂ |Â

up vote
5
down vote

05AB1E, 8 6 bytes

ÃƒÂ¦2ÃƒÂ¹P.M

-2 bytes thanks to @Kaldo.

Try it online or verify all test cases.

Explanation:

ÃƒÂ¦ # Take the powerset of the input-list
 # i.e. [2,3,3] Ã¢Â†Â’ [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]]
 2ÃƒÂ¹ # Leave only the inner lists of size 2:
 # i.e. [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]] Ã¢Â†Â’ [[2,3],[2,3],[3,3]]
 P # Take the product of each remaining pair
 # i.e. [[2,3],[2,3],[3,3]] Ã¢Â†Â’ [6,6,9]
 .M # Only leave the most frequent value(s) in the list
 # i.e. [6,6,9] Ã¢Â†Â’ [6]

edited Aug 6 at 12:30

answered Aug 6 at 12:05

Kevin Cruijssen

28.1k546158

1

Ã¦2Ã¹P.M for 6 bytes
â€“Â Kaldo
Aug 6 at 12:22

@Kaldo Thanks! Completely forgot about Ã¹.
â€“Â Kevin Cruijssen
Aug 6 at 12:30

add a commentÂ |Â

up vote
5
down vote

Perl 6, 41 bytes

key max bag(@_ X*@_)Ã¢ÂˆÂ–@_Ã‚Â»Ã‚Â²: *.value:

Try it online!

edited Aug 6 at 23:20

answered Aug 6 at 11:19

nwellnhof

3,053613

Could you please explain to me (or point me to the docs) what are the colons doing there? I can't quite make it out... I can see that it has something to do with argument passing but nothing more.
â€“Â Ramillies
Aug 6 at 22:08

1

@Ramillies That's the infix : operator.
â€“Â nwellnhof
Aug 6 at 23:18

Ah, I see. Thank you.
â€“Â Ramillies
Aug 6 at 23:22

add a commentÂ |Â

up vote
5
down vote

MATLAB, 43 bytes

I=input('');i=I'*I*1-eye(nnz(I));mode(i(:))

It's also kind of a tongue twister!

Explanation

I=input(''); % Takes an input like "[2,3,4,5,6]"
i=I'*I % Multiplies the input by its own transverse
 *1-eye(nnz(I)); % Multiplies by 1-identity matrix to remove diagonal
mode(i(:)) % Calculates most common value and prints it

edited Aug 7 at 8:22

answered Aug 6 at 16:02

Jacob Watson

1313

i am not sure you need to do I'*I*1-eye Why not just I'*I-eye?
â€“Â aaaaaa
Aug 8 at 0:45

add a commentÂ |Â

up vote
4
down vote

Stax, 12 10 bytes

Ã¢Â•Â¢ÃƒÂªv^Ã¢ÂŒÂÃƒÂ¶Ã¢Â–ÂºÃ¢Â™Â£ÃƒÂ„Ã‚Â»

Run and debug it

edited Aug 6 at 11:27

answered Aug 6 at 11:13

wastl

1,884424

add a commentÂ |Â

up vote
4
down vote

Python 3, 77 72 bytes

f=lambda k,*l,m=:l and f(*l,m=m+[k*x for x in l])or max(m,key=m.count)

Try it online!

edited Aug 6 at 12:42

answered Aug 6 at 11:53

ovs

16.6k2956

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up vote
4
down vote

JavaScript (ES6), 72 70 bytes

a=>a.map(m=o=(y,Y)=>a.map(x=>Y--<0?m=(o[x*=y]=-~o[x])<m?m:o[r=x]:0))|r

Try it online!

edited Aug 6 at 23:13

answered Aug 6 at 11:18

Arnauld

61.6k575258

add a commentÂ |Â

up vote
3
down vote

Charcoal, 24 bytes

Ã¯Â¼Â·ÃŽÂ¸Ã¯Â¼Â¦ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸Ã¢ÂŠÂžÃÂ…ÃŽÂºÃ¯Â¼Â©Ã¢ÂŠÂŸÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Try it online! Link is to verbose version of code. Explanation:

Ã¯Â¼Â·ÃŽÂ¸

While the input array is non-empty...

ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸

... pop the last element and multiply the rest of the array by that element...

Ã¯Â¼Â¦...Ã¢ÂŠÂžÃÂ…ÃŽÂº

... and push the results to the predefined empty list.

Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Count the number of times each product appears in the list and take the maximum...

ÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹...

... then filter for the products whose count equals that maximum...

Ã¯Â¼Â©Ã¢ÂŠÂŸ

...then pop the last element and cast to string for implicit print.

answered Aug 6 at 13:41

Neil

74k743169

add a commentÂ |Â

up vote
3
down vote

Attache, 59 bytes

Last##~SortBy#`&&:`~##Flat[UpperTriangle&1!Table&_!`*]^^0

Try it online!

Still working on golfing this down a bit, but I think this is near optimal for the approach I've chosen.

Explanation

This is a composition of three functions:

Flat[UpperTriangle&1!Table&_!`*]^^0

SortBy#`&&:`~

Last

The first function does the bulk of the computation:

Flat[UpperTriangle&1!Table&_!`*]^^0
 anonymous lambda; input: _ (e.g.: [2,3,4,5,6])
 Table&_!`* shorthand for Table[`*, _]
 this creates a multiplication table using the input
 e.g.:
 4 6 8 10 12
 6 9 12 15 18
 8 12 16 20 24
 10 15 20 25 30
 12 18 24 30 36

 UpperTriangle&1! takes the strict upper triangle of this matrix
 e.g.:
 0 6 8 10 12
 0 0 12 15 18
 0 0 0 20 24
 0 0 0 0 30
 0 0 0 0 0
Flat[ ]^^0 flattens this list and removes all 0s
 e.g.: [6, 8, 10, 12, 12, 15, 18, 20, 24, 30]

The second is a bit complicated but does something rather simple. First, it is useful to know that f&n is a function which, when called with arguments ...x, returns f[...x, n]. f&:n is similar, returning f[n, ...x]. Now, let's decompose this:

( ~SortBy ) # (`& &: `~)

First, f#g creates a fork. With input n, it returns f[n, g[n]]. However, in this case, f is the function ~SortBy. ~f reverses the arguments of the function. This means that ~f#g is equivalent to f[g[n], n], or here, SortBy[(`& &: `~)[n], n].

`& &: `~ follows the form f&:n. But what are `& and `~? They are "operator quotes", and return a function equivalent to the quoted operator. So, in this case, `& is the same thing as $ x & y . With that in mind, this expression is equivalent to the following for binary operators:

f&:n <=> $ f[n, x] 
 <=> $ (`&)[`~, x] 
 <=> $ `~ & x

This yields the function `~&x, where x is the result from the first function. n ~ a counts the occurrences of n in a. So, this returns a function which counts the occurrences of the argument in the computed array from function 1.

Going back to SortBy, this each element in the array by the number of times it appears in it.

Finally, Last takes the element which occurs the most. Ties are broken by the sorting algorithm.

answered Aug 6 at 18:24

Conor O'Brien

27.9k262156

Is the UpperTriangle part required? Can you just flatten the table and sort?
â€“Â svavil
Aug 7 at 12:14

@svavil Yes, it is required; [5, 2, 9, 10, 3, 4, 4, 4, 7] -> 16 instead of 20 without it.
â€“Â Conor O'Brien
Aug 7 at 18:41

add a commentÂ |Â

up vote
3
down vote

APL (Dyalog Unicode), 29 27 19 bytes

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚

Try it online!

Tacit fn.

Thanks to AdÃƒÂ¡m for the tacit version and 2 bytes.

Thanks to ngn for 8 bytes!

How:

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚
 Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚ Ã¢ÂÂ Multiply each element with the entire argument, then
 Ã¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨ Ã¢ÂÂ Remove 1 from the first, two from the next etc. (removes repeated multiplications);
 Ã¢ÂÂ The result is then fed into the function:
 Ã¢ÂˆÂŠÃ¢ÂÂµ Ã¢ÂÂ Flatten the result;
 Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸ Ã¢ÂÂ Key; creates a matrix in which each row corresponds to a unique product;
 Ã¢ÂŠÂ¢/ Ã¢ÂÂ Get the rightmost column of the matrix;
 Ã¢ÂŒÂˆ/ Ã¢ÂÂ Get the highest value.

edited Aug 7 at 18:23

answered Aug 7 at 14:48

J. SallÃ©

1,298218

1

This is only 27.
â€“Â AdÃ¡m
Aug 7 at 15:18

add a commentÂ |Â

up vote
3
down vote

CJam, 70 68 bytes

q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

Try it online!

Explanation

q',/S*~ Turn input string into a valid CJam array
 _,( Find the length of the array and subtract 1
 :L Assign the result to L
 fX Outer for loop
 LX-,0a+[X1++*](; Create an array with all the array indexes bigger than X
 fY Inner for loop
 _X=_Y=@* Create a multiple of array[X] and array[Y] (Guaranteed to be from a unique combination of factors)
 ~;] Casts away all stack items except for an array of the multiples
 __@e=$; Sorts array by number of occurrences (largest number of occurences at the end)
 _,(= Gets the last element of the array

You will need to scroll right to see the explanations as the code is quite long, as well as the explanations.

This was an absolute nightmare to write. CJam doesn't have a powerset function (unlike a ton of other golfing languages - great choice on my part), which means that I had to manually find the powerset. However, this gave me the opportunity to ignore any invalid number of factors, unlike other answers with a powerset function.

This should be golfable, considering I'm terrible at CJam.

Changes:

Helen cut off 2 bytes!

Old: q',/S*~_,1-:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,1-=

New: q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

By changing the 1-s to simply ( we get the same effect but with a lower byte count.

edited Aug 8 at 18:37

answered Aug 7 at 23:21

Helen

1055

add a commentÂ |Â

up vote
2
down vote

Java (JDK 10), 132 bytes

a->int l=a.length,i=l,j=0,r=99999,m=new int[r];for(;i-->0;)for(j=l;--j>i;)m[a[i]*a[j]]++;for(;r-->0;)i=m[r]<i?i:m[j=r];return j;

Try it online!

answered Aug 7 at 8:35

Olivier GrÃ©goire

7,37311739

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up vote
2
down vote

Japt `-h`, 20 bytes

Not the best. I dont know how to make this code shorter

Ã‚Â£UsYÃƒÂ„ Ã‚Â®*X
c n ÃƒÂ³Ã‚Â¥ ÃƒÂ±ÃƒÂŠo

Try it online!

answered Aug 7 at 15:12

Luis felipe De jesus Munoz

2,4451039

add a commentÂ |Â

up vote
2
down vote

Husk, 7 bytes

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2

Try it online!

Explanation

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2 -- example input [3,3,3]
 Ã¡Â¹Â–2 -- subsequences of length 2: [[3,3],[3,3],[3,3]]
 mÃŽÂ  -- map product: [9,9,9]
Ã¡Â¹Â  -- apply 
 # -- | count occurences in list
 Ã¢Â–Âº -- to maxOn that list: [9]

answered Aug 7 at 15:34

BWO

9,06111569

add a commentÂ |Â

up vote
2
down vote

Haskell, 96 94 bytes

^{-2 bytes thanks to nimi (using sortOn(0<$) instead of length)!}

import Data.List
f a|b<-zip[0..]a=last.last.sortOn(0<$).group$sort[x*y|(i,x)<-b,(j,y)<-b,i/=j]

Try it online!

edited Aug 7 at 19:29

answered Aug 7 at 15:50

BWO

9,06111569

1

sortOn(0<$).
â€“Â nimi
Aug 7 at 19:26

add a commentÂ |Â

up vote
2
down vote

MATLAB 39 bytes

a=input('');
b=triu(a'*a,1);
mode(b(b~=0))

Also check out answer by Jacob Watson

edited Aug 8 at 14:48

answered Aug 8 at 0:40

aaaaaa

2816

1

Having the second line be b=triu(a'*a,1); saves 4 bytes.
â€“Â sundar
Aug 8 at 12:32

@sundar Oh snap, you are right :) I had triu intially but drifted away somehow
â€“Â aaaaaa
Aug 8 at 14:47

Good solution, I didn't realise the upper triangle function was so short!
â€“Â Jacob Watson
Aug 10 at 8:19

add a commentÂ |Â

up vote
2
down vote

SQL Server, 93 bytes

SELECT TOP 1a.a*b.a
FROM @ a
JOIN @ b ON a.i<b.i
GROUP BY a.a*b.a
ORDER BY COUNT(a.a*b.a)DESC

Input is assumed to come from a table of the form

DECLARE @ TABLE (A int, i int identity);

Example table population:

INSERT INTO @ VALUES (9), (7), (10), (9), (7), (8), (5), (10), (1);

Explanation:

I assume a "list of integers" will have an index associated with them, which in my case is the column i. The column a contains the values of the list.

I create products of every pair, where the left pair comes in the list earlier than the right pair. I then group on the product, and sort by the most populous number.

I'm a little sad I didn't get to use any cte or partitioning clauses, but they were just too long. SELECT is a very expensive keyword.

Alternative, 183 bytes

WITH c
AS(SELECT a,ROW_NUMBER()OVER(ORDER BY a)r
FROM @),d AS(SELECT a.a*b.a p,COUNT(a.a*b.a)m
FROM c a
JOIN c b ON a.r<b.r GROUP BY a.a*b.a)SELECT TOP 1p
FROM d
ORDER BY m DESC

If SQL doesn't get to have a separate index column, here is a solution where I create an index using the ROW_NUMBER function. I personally don't care about the order, but an order is required and using the a column is the shortest.

answered Aug 8 at 17:52

Brian J

653613

add a commentÂ |Â

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Name

22 Answers
22

active

oldest

votes

22 Answers
22

active

oldest

votes

up vote
10
down vote

R, 54 50 41 bytes

order(-tabulate(combn(scan(),2,prod)))[1]

Try it online!

Alternatively, for 54 53 44 bytes:

names(sort(-table(combn(scan(),2,prod))))[1]

Try it online!

In principle, the latter version outputs the relevant result even without the names function, but followed by the count of such most frequent products, which isn't asked for...

Thanks to CriminallyVulgar for -4 and -1, and Giuseppe for -9 on both.

edited Aug 6 at 13:29

answered Aug 6 at 12:50

Kirill L.

2,0961114

1

On the second on you can use -table() instead of descending=TRUE for -1. I really like the cleverness of the first one though. EDIT: Just realised you can also apply that to the first one for -4, so there's that. Try it online!
â€“Â CriminallyVulgar
Aug 6 at 12:59

1

combn(scan(),2,prod) works instead of using apply
â€“Â Giuseppe
Aug 6 at 13:24

add a commentÂ |Â

up vote
10
down vote

R, 54 50 41 bytes

order(-tabulate(combn(scan(),2,prod)))[1]

Try it online!

Alternatively, for 54 53 44 bytes:

names(sort(-table(combn(scan(),2,prod))))[1]

Try it online!

In principle, the latter version outputs the relevant result even without the names function, but followed by the count of such most frequent products, which isn't asked for...

Thanks to CriminallyVulgar for -4 and -1, and Giuseppe for -9 on both.

edited Aug 6 at 13:29

answered Aug 6 at 12:50

Kirill L.

2,0961114

1

On the second on you can use -table() instead of descending=TRUE for -1. I really like the cleverness of the first one though. EDIT: Just realised you can also apply that to the first one for -4, so there's that. Try it online!
â€“Â CriminallyVulgar
Aug 6 at 12:59

1

combn(scan(),2,prod) works instead of using apply
â€“Â Giuseppe
Aug 6 at 13:24

add a commentÂ |Â

up vote
10
down vote

R, 54 50 41 bytes

order(-tabulate(combn(scan(),2,prod)))[1]

Try it online!

Alternatively, for 54 53 44 bytes:

names(sort(-table(combn(scan(),2,prod))))[1]

Try it online!

In principle, the latter version outputs the relevant result even without the names function, but followed by the count of such most frequent products, which isn't asked for...

Thanks to CriminallyVulgar for -4 and -1, and Giuseppe for -9 on both.

edited Aug 6 at 13:29

answered Aug 6 at 12:50

Kirill L.

2,0961114

R, 54 50 41 bytes

order(-tabulate(combn(scan(),2,prod)))[1]

Try it online!

Alternatively, for 54 53 44 bytes:

names(sort(-table(combn(scan(),2,prod))))[1]

Try it online!

In principle, the latter version outputs the relevant result even without the names function, but followed by the count of such most frequent products, which isn't asked for...

Thanks to CriminallyVulgar for -4 and -1, and Giuseppe for -9 on both.

edited Aug 6 at 13:29

answered Aug 6 at 12:50

Kirill L.

2,0961114

edited Aug 6 at 13:29

answered Aug 6 at 12:50

Kirill L.

2,0961114

answered Aug 6 at 12:50

Kirill L.

2,0961114

answered Aug 6 at 12:50

Kirill L.

2,0961114

1

On the second on you can use -table() instead of descending=TRUE for -1. I really like the cleverness of the first one though. EDIT: Just realised you can also apply that to the first one for -4, so there's that. Try it online!
â€“Â CriminallyVulgar
Aug 6 at 12:59

1

combn(scan(),2,prod) works instead of using apply
â€“Â Giuseppe
Aug 6 at 13:24

add a commentÂ |Â

1

On the second on you can use -table() instead of descending=TRUE for -1. I really like the cleverness of the first one though. EDIT: Just realised you can also apply that to the first one for -4, so there's that. Try it online!
â€“Â CriminallyVulgar
Aug 6 at 12:59

1

combn(scan(),2,prod) works instead of using apply
â€“Â Giuseppe
Aug 6 at 13:24

On the second on you can use -table() instead of descending=TRUE for -1. I really like the cleverness of the first one though. EDIT: Just realised you can also apply that to the first one for -4, so there's that. Try it online!
â€“Â CriminallyVulgar
Aug 6 at 12:59

combn(scan(),2,prod) works instead of using apply
â€“Â Giuseppe
Aug 6 at 13:24

add a commentÂ |Â

up vote
8
down vote

Brachylog, 11 bytes

Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ—Ã¡Â¶Â Ã¡Â»ÂtÃ¡ÂµÂ’th

Try it online!

Explanation

 Ã¡Â¶Â  Find all:
 Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ— Product of a subset of 2 elements
 Ã¡Â»ÂtÃ¡ÂµÂ’ Order by occurrences
 th Take the last element and discard the number of occurrences

answered Aug 6 at 11:23

Fatalize

26.5k448133

I don't know how code golf usually works but aren't some of these characters outside the standard 256 code points and therefore multiple bytes each?
â€“Â Holloway
Aug 7 at 12:02

2

@Holloway Brachylog uses a custom code page
â€“Â Fatalize
Aug 7 at 12:07

add a commentÂ |Â

up vote
8
down vote

Brachylog, 11 bytes

Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ—Ã¡Â¶Â Ã¡Â»ÂtÃ¡ÂµÂ’th

Try it online!

Explanation

 Ã¡Â¶Â  Find all:
 Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ— Product of a subset of 2 elements
 Ã¡Â»ÂtÃ¡ÂµÂ’ Order by occurrences
 th Take the last element and discard the number of occurrences

answered Aug 6 at 11:23

Fatalize

26.5k448133

I don't know how code golf usually works but aren't some of these characters outside the standard 256 code points and therefore multiple bytes each?
â€“Â Holloway
Aug 7 at 12:02

2

@Holloway Brachylog uses a custom code page
â€“Â Fatalize
Aug 7 at 12:07

add a commentÂ |Â

up vote
8
down vote

Brachylog, 11 bytes

Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ—Ã¡Â¶Â Ã¡Â»ÂtÃ¡ÂµÂ’th

Try it online!

Explanation

 Ã¡Â¶Â  Find all:
 Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ— Product of a subset of 2 elements
 Ã¡Â»ÂtÃ¡ÂµÂ’ Order by occurrences
 th Take the last element and discard the number of occurrences

answered Aug 6 at 11:23

Fatalize

26.5k448133

Brachylog, 11 bytes

Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ—Ã¡Â¶Â Ã¡Â»ÂtÃ¡ÂµÂ’th

Try it online!

Explanation

 Ã¡Â¶Â  Find all:
 Ã¢ÂŠÂ‡Ã„ÂŠÃƒÂ— Product of a subset of 2 elements
 Ã¡Â»ÂtÃ¡ÂµÂ’ Order by occurrences
 th Take the last element and discard the number of occurrences

answered Aug 6 at 11:23

Fatalize

26.5k448133

answered Aug 6 at 11:23

Fatalize

26.5k448133

answered Aug 6 at 11:23

Fatalize

26.5k448133

answered Aug 6 at 11:23

Fatalize

26.5k448133

I don't know how code golf usually works but aren't some of these characters outside the standard 256 code points and therefore multiple bytes each?
â€“Â Holloway
Aug 7 at 12:02

2

@Holloway Brachylog uses a custom code page
â€“Â Fatalize
Aug 7 at 12:07

add a commentÂ |Â

I don't know how code golf usually works but aren't some of these characters outside the standard 256 code points and therefore multiple bytes each?
â€“Â Holloway
Aug 7 at 12:02

2

@Holloway Brachylog uses a custom code page
â€“Â Fatalize
Aug 7 at 12:07

I don't know how code golf usually works but aren't some of these characters outside the standard 256 code points and therefore multiple bytes each?
â€“Â Holloway
Aug 7 at 12:02

@Holloway Brachylog uses a custom code page
â€“Â Fatalize
Aug 7 at 12:07

add a commentÂ |Â

up vote
6
down vote

Pyth, 12 bytes

eo/QN=*M.cQ2

Test suite

answered Aug 6 at 10:51

isaacg

34.4k553185

add a commentÂ |Â

up vote
6
down vote

Pyth, 12 bytes

eo/QN=*M.cQ2

Test suite

answered Aug 6 at 10:51

isaacg

34.4k553185

add a commentÂ |Â

up vote
6
down vote

Pyth, 12 bytes

eo/QN=*M.cQ2

Test suite

answered Aug 6 at 10:51

isaacg

34.4k553185

Pyth, 12 bytes

eo/QN=*M.cQ2

Test suite

answered Aug 6 at 10:51

isaacg

34.4k553185

answered Aug 6 at 10:51

isaacg

34.4k553185

answered Aug 6 at 10:51

isaacg

34.4k553185

answered Aug 6 at 10:51

isaacg

34.4k553185

add a commentÂ |Â

up vote
6
down vote

MATL, 8 7 bytes

2XN!pXM

Try it online!

(-1 byte by using the method from @Mr. Xcoder's Jelly answer.)

2XN % nchoosek - get all combinations of 2 elements from input
!p % get the product of each combination
XM % 'mode': get the most common value from that

Older answer:

8 bytes

&*XRXzXM

Try it online!

&* % multiply input by its transpose,
 % getting all elementwise products
XR % take the upper-triangular portion of that,
 % zeroing out repetitions and mainly self-multiplications
Xz % remove the zeroed out parts
XM % 'mode' calculation - get the most common value from that

edited Aug 6 at 13:37

answered Aug 6 at 13:27

sundar

4,383828

add a commentÂ |Â

up vote
6
down vote

MATL, 8 7 bytes

2XN!pXM

Try it online!

(-1 byte by using the method from @Mr. Xcoder's Jelly answer.)

2XN % nchoosek - get all combinations of 2 elements from input
!p % get the product of each combination
XM % 'mode': get the most common value from that

Older answer:

8 bytes

&*XRXzXM

Try it online!

&* % multiply input by its transpose,
 % getting all elementwise products
XR % take the upper-triangular portion of that,
 % zeroing out repetitions and mainly self-multiplications
Xz % remove the zeroed out parts
XM % 'mode' calculation - get the most common value from that

edited Aug 6 at 13:37

answered Aug 6 at 13:27

sundar

4,383828

add a commentÂ |Â

up vote
6
down vote

MATL, 8 7 bytes

2XN!pXM

Try it online!

(-1 byte by using the method from @Mr. Xcoder's Jelly answer.)

2XN % nchoosek - get all combinations of 2 elements from input
!p % get the product of each combination
XM % 'mode': get the most common value from that

Older answer:

8 bytes

&*XRXzXM

Try it online!

&* % multiply input by its transpose,
 % getting all elementwise products
XR % take the upper-triangular portion of that,
 % zeroing out repetitions and mainly self-multiplications
Xz % remove the zeroed out parts
XM % 'mode' calculation - get the most common value from that

edited Aug 6 at 13:37

answered Aug 6 at 13:27

sundar

4,383828

MATL, 8 7 bytes

2XN!pXM

Try it online!

(-1 byte by using the method from @Mr. Xcoder's Jelly answer.)

2XN % nchoosek - get all combinations of 2 elements from input
!p % get the product of each combination
XM % 'mode': get the most common value from that

Older answer:

8 bytes

&*XRXzXM

Try it online!

&* % multiply input by its transpose,
 % getting all elementwise products
XR % take the upper-triangular portion of that,
 % zeroing out repetitions and mainly self-multiplications
Xz % remove the zeroed out parts
XM % 'mode' calculation - get the most common value from that

edited Aug 6 at 13:37

answered Aug 6 at 13:27

sundar

4,383828

edited Aug 6 at 13:37

answered Aug 6 at 13:27

sundar

4,383828

answered Aug 6 at 13:27

sundar

4,383828

answered Aug 6 at 13:27

sundar

4,383828

add a commentÂ |Â

up vote
6
down vote

Mathematica, 32 bytes

^{-17 bytes (and a fix) thanks to JungHwan Min.}

Commonest[1##&@@@#~Subsets~2]&

Pure function. Takes a list of numbers as input and returns the list of MCMs as output.

edited Aug 7 at 1:29

answered Aug 6 at 10:53

LegionMammal978

14.7k41752

Actually it looks like both of us misread the question. This fails for input 3, 3, 3. Fixed: Commonest[1##&@@@#~Subsets~2]&
â€“Â JungHwan Min
Aug 6 at 20:21

@JungHwanMin Huh. I thought that Subsets didn't count repeats as separate elements. It seems like it does, though, so thanks!
â€“Â LegionMammal978
Aug 7 at 1:28

add a commentÂ |Â

up vote
6
down vote

Mathematica, 32 bytes

^{-17 bytes (and a fix) thanks to JungHwan Min.}

Commonest[1##&@@@#~Subsets~2]&

Pure function. Takes a list of numbers as input and returns the list of MCMs as output.

edited Aug 7 at 1:29

answered Aug 6 at 10:53

LegionMammal978

14.7k41752

Actually it looks like both of us misread the question. This fails for input 3, 3, 3. Fixed: Commonest[1##&@@@#~Subsets~2]&
â€“Â JungHwan Min
Aug 6 at 20:21

@JungHwanMin Huh. I thought that Subsets didn't count repeats as separate elements. It seems like it does, though, so thanks!
â€“Â LegionMammal978
Aug 7 at 1:28

add a commentÂ |Â

up vote
6
down vote

Mathematica, 32 bytes

^{-17 bytes (and a fix) thanks to JungHwan Min.}

Commonest[1##&@@@#~Subsets~2]&

Pure function. Takes a list of numbers as input and returns the list of MCMs as output.

edited Aug 7 at 1:29

answered Aug 6 at 10:53

LegionMammal978

14.7k41752

Mathematica, 32 bytes

^{-17 bytes (and a fix) thanks to JungHwan Min.}

Commonest[1##&@@@#~Subsets~2]&

Pure function. Takes a list of numbers as input and returns the list of MCMs as output.

edited Aug 7 at 1:29

answered Aug 6 at 10:53

LegionMammal978

14.7k41752

edited Aug 7 at 1:29

answered Aug 6 at 10:53

LegionMammal978

14.7k41752

answered Aug 6 at 10:53

LegionMammal978

14.7k41752

answered Aug 6 at 10:53

LegionMammal978

14.7k41752

Actually it looks like both of us misread the question. This fails for input 3, 3, 3. Fixed: Commonest[1##&@@@#~Subsets~2]&
â€“Â JungHwan Min
Aug 6 at 20:21

@JungHwanMin Huh. I thought that Subsets didn't count repeats as separate elements. It seems like it does, though, so thanks!
â€“Â LegionMammal978
Aug 7 at 1:28

add a commentÂ |Â

Actually it looks like both of us misread the question. This fails for input 3, 3, 3. Fixed: Commonest[1##&@@@#~Subsets~2]&
â€“Â JungHwan Min
Aug 6 at 20:21

@JungHwanMin Huh. I thought that Subsets didn't count repeats as separate elements. It seems like it does, though, so thanks!
â€“Â LegionMammal978
Aug 7 at 1:28

Actually it looks like both of us misread the question. This fails for input 3, 3, 3. Fixed: Commonest[1##&@@@#~Subsets~2]&
â€“Â JungHwan Min
Aug 6 at 20:21

@JungHwanMin Huh. I thought that Subsets didn't count repeats as separate elements. It seems like it does, though, so thanks!
â€“Â LegionMammal978
Aug 7 at 1:28

add a commentÂ |Â

up vote
5
down vote

Jelly, 6 bytes

Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ

Try it online! or Check out the test suite.

How it works


Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Full program / Monadic link.
Ã…Â’c Ã¢Â€Â“ Unordered pairs without replacement.
 PÃ¢Â‚Â¬ Ã¢Â€Â“ Product of each.
 ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Mode (most common element).

Alternative: Ã…Â’cZPÃƒÂ†Ã¡Â¹Âƒ

edited Aug 6 at 11:18

answered Aug 6 at 11:10

Mr. Xcoder

29.4k756192

add a commentÂ |Â

up vote
5
down vote

Jelly, 6 bytes

Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ

Try it online! or Check out the test suite.

How it works


Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Full program / Monadic link.
Ã…Â’c Ã¢Â€Â“ Unordered pairs without replacement.
 PÃ¢Â‚Â¬ Ã¢Â€Â“ Product of each.
 ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Mode (most common element).

Alternative: Ã…Â’cZPÃƒÂ†Ã¡Â¹Âƒ

edited Aug 6 at 11:18

answered Aug 6 at 11:10

Mr. Xcoder

29.4k756192

add a commentÂ |Â

up vote
5
down vote

Jelly, 6 bytes

Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ

Try it online! or Check out the test suite.

How it works


Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Full program / Monadic link.
Ã…Â’c Ã¢Â€Â“ Unordered pairs without replacement.
 PÃ¢Â‚Â¬ Ã¢Â€Â“ Product of each.
 ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Mode (most common element).

Alternative: Ã…Â’cZPÃƒÂ†Ã¡Â¹Âƒ

edited Aug 6 at 11:18

answered Aug 6 at 11:10

Mr. Xcoder

29.4k756192

Jelly, 6 bytes

Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ

Try it online! or Check out the test suite.

How it works


Ã…Â’cPÃ¢Â‚Â¬ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Full program / Monadic link.
Ã…Â’c Ã¢Â€Â“ Unordered pairs without replacement.
 PÃ¢Â‚Â¬ Ã¢Â€Â“ Product of each.
 ÃƒÂ†Ã¡Â¹Âƒ Ã¢Â€Â“ Mode (most common element).

Alternative: Ã…Â’cZPÃƒÂ†Ã¡Â¹Âƒ

edited Aug 6 at 11:18

answered Aug 6 at 11:10

Mr. Xcoder

29.4k756192

edited Aug 6 at 11:18

answered Aug 6 at 11:10

Mr. Xcoder

29.4k756192

answered Aug 6 at 11:10

Mr. Xcoder

29.4k756192

answered Aug 6 at 11:10

Mr. Xcoder

29.4k756192

add a commentÂ |Â

up vote
5
down vote

05AB1E, 8 6 bytes

ÃƒÂ¦2ÃƒÂ¹P.M

-2 bytes thanks to @Kaldo.

Try it online or verify all test cases.

Explanation:

ÃƒÂ¦ # Take the powerset of the input-list
 # i.e. [2,3,3] Ã¢Â†Â’ [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]]
 2ÃƒÂ¹ # Leave only the inner lists of size 2:
 # i.e. [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]] Ã¢Â†Â’ [[2,3],[2,3],[3,3]]
 P # Take the product of each remaining pair
 # i.e. [[2,3],[2,3],[3,3]] Ã¢Â†Â’ [6,6,9]
 .M # Only leave the most frequent value(s) in the list
 # i.e. [6,6,9] Ã¢Â†Â’ [6]

edited Aug 6 at 12:30

answered Aug 6 at 12:05

Kevin Cruijssen

28.1k546158

1

Ã¦2Ã¹P.M for 6 bytes
â€“Â Kaldo
Aug 6 at 12:22

@Kaldo Thanks! Completely forgot about Ã¹.
â€“Â Kevin Cruijssen
Aug 6 at 12:30

add a commentÂ |Â

up vote
5
down vote

05AB1E, 8 6 bytes

ÃƒÂ¦2ÃƒÂ¹P.M

-2 bytes thanks to @Kaldo.

Try it online or verify all test cases.

Explanation:

ÃƒÂ¦ # Take the powerset of the input-list
 # i.e. [2,3,3] Ã¢Â†Â’ [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]]
 2ÃƒÂ¹ # Leave only the inner lists of size 2:
 # i.e. [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]] Ã¢Â†Â’ [[2,3],[2,3],[3,3]]
 P # Take the product of each remaining pair
 # i.e. [[2,3],[2,3],[3,3]] Ã¢Â†Â’ [6,6,9]
 .M # Only leave the most frequent value(s) in the list
 # i.e. [6,6,9] Ã¢Â†Â’ [6]

edited Aug 6 at 12:30

answered Aug 6 at 12:05

Kevin Cruijssen

28.1k546158

1

Ã¦2Ã¹P.M for 6 bytes
â€“Â Kaldo
Aug 6 at 12:22

@Kaldo Thanks! Completely forgot about Ã¹.
â€“Â Kevin Cruijssen
Aug 6 at 12:30

add a commentÂ |Â

up vote
5
down vote

05AB1E, 8 6 bytes

ÃƒÂ¦2ÃƒÂ¹P.M

-2 bytes thanks to @Kaldo.

Try it online or verify all test cases.

Explanation:

ÃƒÂ¦ # Take the powerset of the input-list
 # i.e. [2,3,3] Ã¢Â†Â’ [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]]
 2ÃƒÂ¹ # Leave only the inner lists of size 2:
 # i.e. [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]] Ã¢Â†Â’ [[2,3],[2,3],[3,3]]
 P # Take the product of each remaining pair
 # i.e. [[2,3],[2,3],[3,3]] Ã¢Â†Â’ [6,6,9]
 .M # Only leave the most frequent value(s) in the list
 # i.e. [6,6,9] Ã¢Â†Â’ [6]

edited Aug 6 at 12:30

answered Aug 6 at 12:05

Kevin Cruijssen

28.1k546158

05AB1E, 8 6 bytes

ÃƒÂ¦2ÃƒÂ¹P.M

-2 bytes thanks to @Kaldo.

Try it online or verify all test cases.

Explanation:

ÃƒÂ¦ # Take the powerset of the input-list
 # i.e. [2,3,3] Ã¢Â†Â’ [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]]
 2ÃƒÂ¹ # Leave only the inner lists of size 2:
 # i.e. [,[2],[3],[3],[2,3],[2,3],[3,3],[2,3,3]] Ã¢Â†Â’ [[2,3],[2,3],[3,3]]
 P # Take the product of each remaining pair
 # i.e. [[2,3],[2,3],[3,3]] Ã¢Â†Â’ [6,6,9]
 .M # Only leave the most frequent value(s) in the list
 # i.e. [6,6,9] Ã¢Â†Â’ [6]

edited Aug 6 at 12:30

answered Aug 6 at 12:05

Kevin Cruijssen

28.1k546158

edited Aug 6 at 12:30

answered Aug 6 at 12:05

Kevin Cruijssen

28.1k546158

answered Aug 6 at 12:05

Kevin Cruijssen

28.1k546158

answered Aug 6 at 12:05

Kevin Cruijssen

28.1k546158

1

Ã¦2Ã¹P.M for 6 bytes
â€“Â Kaldo
Aug 6 at 12:22

@Kaldo Thanks! Completely forgot about Ã¹.
â€“Â Kevin Cruijssen
Aug 6 at 12:30

add a commentÂ |Â

1

Ã¦2Ã¹P.M for 6 bytes
â€“Â Kaldo
Aug 6 at 12:22

@Kaldo Thanks! Completely forgot about Ã¹.
â€“Â Kevin Cruijssen
Aug 6 at 12:30

Ã¦2Ã¹P.M for 6 bytes
â€“Â Kaldo
Aug 6 at 12:22

@Kaldo Thanks! Completely forgot about Ã¹.
â€“Â Kevin Cruijssen
Aug 6 at 12:30

add a commentÂ |Â

up vote
5
down vote

Perl 6, 41 bytes

key max bag(@_ X*@_)Ã¢ÂˆÂ–@_Ã‚Â»Ã‚Â²: *.value:

Try it online!

edited Aug 6 at 23:20

answered Aug 6 at 11:19

nwellnhof

3,053613

Could you please explain to me (or point me to the docs) what are the colons doing there? I can't quite make it out... I can see that it has something to do with argument passing but nothing more.
â€“Â Ramillies
Aug 6 at 22:08

1

@Ramillies That's the infix : operator.
â€“Â nwellnhof
Aug 6 at 23:18

Ah, I see. Thank you.
â€“Â Ramillies
Aug 6 at 23:22

add a commentÂ |Â

up vote
5
down vote

Perl 6, 41 bytes

key max bag(@_ X*@_)Ã¢ÂˆÂ–@_Ã‚Â»Ã‚Â²: *.value:

Try it online!

edited Aug 6 at 23:20

answered Aug 6 at 11:19

nwellnhof

3,053613

Could you please explain to me (or point me to the docs) what are the colons doing there? I can't quite make it out... I can see that it has something to do with argument passing but nothing more.
â€“Â Ramillies
Aug 6 at 22:08

1

@Ramillies That's the infix : operator.
â€“Â nwellnhof
Aug 6 at 23:18

Ah, I see. Thank you.
â€“Â Ramillies
Aug 6 at 23:22

add a commentÂ |Â

up vote
5
down vote

Perl 6, 41 bytes

key max bag(@_ X*@_)Ã¢ÂˆÂ–@_Ã‚Â»Ã‚Â²: *.value:

Try it online!

edited Aug 6 at 23:20

answered Aug 6 at 11:19

nwellnhof

3,053613

Perl 6, 41 bytes

key max bag(@_ X*@_)Ã¢ÂˆÂ–@_Ã‚Â»Ã‚Â²: *.value:

Try it online!

edited Aug 6 at 23:20

answered Aug 6 at 11:19

nwellnhof

3,053613

edited Aug 6 at 23:20

answered Aug 6 at 11:19

nwellnhof

3,053613

answered Aug 6 at 11:19

nwellnhof

3,053613

answered Aug 6 at 11:19

nwellnhof

3,053613

Could you please explain to me (or point me to the docs) what are the colons doing there? I can't quite make it out... I can see that it has something to do with argument passing but nothing more.
â€“Â Ramillies
Aug 6 at 22:08

1

@Ramillies That's the infix : operator.
â€“Â nwellnhof
Aug 6 at 23:18

Ah, I see. Thank you.
â€“Â Ramillies
Aug 6 at 23:22

add a commentÂ |Â

Could you please explain to me (or point me to the docs) what are the colons doing there? I can't quite make it out... I can see that it has something to do with argument passing but nothing more.
â€“Â Ramillies
Aug 6 at 22:08

1

@Ramillies That's the infix : operator.
â€“Â nwellnhof
Aug 6 at 23:18

Ah, I see. Thank you.
â€“Â Ramillies
Aug 6 at 23:22

Could you please explain to me (or point me to the docs) what are the colons doing there? I can't quite make it out... I can see that it has something to do with argument passing but nothing more.
â€“Â Ramillies
Aug 6 at 22:08

@Ramillies That's the infix : operator.
â€“Â nwellnhof
Aug 6 at 23:18

Ah, I see. Thank you.
â€“Â Ramillies
Aug 6 at 23:22

add a commentÂ |Â

up vote
5
down vote

MATLAB, 43 bytes

I=input('');i=I'*I*1-eye(nnz(I));mode(i(:))

It's also kind of a tongue twister!

Explanation

I=input(''); % Takes an input like "[2,3,4,5,6]"
i=I'*I % Multiplies the input by its own transverse
 *1-eye(nnz(I)); % Multiplies by 1-identity matrix to remove diagonal
mode(i(:)) % Calculates most common value and prints it

edited Aug 7 at 8:22

answered Aug 6 at 16:02

Jacob Watson

1313

i am not sure you need to do I'*I*1-eye Why not just I'*I-eye?
â€“Â aaaaaa
Aug 8 at 0:45

add a commentÂ |Â

up vote
5
down vote

MATLAB, 43 bytes

I=input('');i=I'*I*1-eye(nnz(I));mode(i(:))

It's also kind of a tongue twister!

Explanation

I=input(''); % Takes an input like "[2,3,4,5,6]"
i=I'*I % Multiplies the input by its own transverse
 *1-eye(nnz(I)); % Multiplies by 1-identity matrix to remove diagonal
mode(i(:)) % Calculates most common value and prints it

edited Aug 7 at 8:22

answered Aug 6 at 16:02

Jacob Watson

1313

i am not sure you need to do I'*I*1-eye Why not just I'*I-eye?
â€“Â aaaaaa
Aug 8 at 0:45

add a commentÂ |Â

up vote
5
down vote

MATLAB, 43 bytes

I=input('');i=I'*I*1-eye(nnz(I));mode(i(:))

It's also kind of a tongue twister!

Explanation

I=input(''); % Takes an input like "[2,3,4,5,6]"
i=I'*I % Multiplies the input by its own transverse
 *1-eye(nnz(I)); % Multiplies by 1-identity matrix to remove diagonal
mode(i(:)) % Calculates most common value and prints it

edited Aug 7 at 8:22

answered Aug 6 at 16:02

Jacob Watson

1313

MATLAB, 43 bytes

I=input('');i=I'*I*1-eye(nnz(I));mode(i(:))

It's also kind of a tongue twister!

Explanation

I=input(''); % Takes an input like "[2,3,4,5,6]"
i=I'*I % Multiplies the input by its own transverse
 *1-eye(nnz(I)); % Multiplies by 1-identity matrix to remove diagonal
mode(i(:)) % Calculates most common value and prints it

edited Aug 7 at 8:22

answered Aug 6 at 16:02

Jacob Watson

1313

edited Aug 7 at 8:22

answered Aug 6 at 16:02

Jacob Watson

1313

answered Aug 6 at 16:02

Jacob Watson

1313

answered Aug 6 at 16:02

Jacob Watson

1313

i am not sure you need to do I'*I*1-eye Why not just I'*I-eye?
â€“Â aaaaaa
Aug 8 at 0:45

add a commentÂ |Â

i am not sure you need to do I'*I*1-eye Why not just I'*I-eye?
â€“Â aaaaaa
Aug 8 at 0:45

i am not sure you need to do I'*I*1-eye Why not just I'*I-eye?
â€“Â aaaaaa
Aug 8 at 0:45

add a commentÂ |Â

up vote
4
down vote

Stax, 12 10 bytes

Ã¢Â•Â¢ÃƒÂªv^Ã¢ÂŒÂÃƒÂ¶Ã¢Â–ÂºÃ¢Â™Â£ÃƒÂ„Ã‚Â»

Run and debug it

edited Aug 6 at 11:27

answered Aug 6 at 11:13

wastl

1,884424

add a commentÂ |Â

up vote
4
down vote

Stax, 12 10 bytes

Ã¢Â•Â¢ÃƒÂªv^Ã¢ÂŒÂÃƒÂ¶Ã¢Â–ÂºÃ¢Â™Â£ÃƒÂ„Ã‚Â»

Run and debug it

edited Aug 6 at 11:27

answered Aug 6 at 11:13

wastl

1,884424

add a commentÂ |Â

up vote
4
down vote

Stax, 12 10 bytes

Ã¢Â•Â¢ÃƒÂªv^Ã¢ÂŒÂÃƒÂ¶Ã¢Â–ÂºÃ¢Â™Â£ÃƒÂ„Ã‚Â»

Run and debug it

edited Aug 6 at 11:27

answered Aug 6 at 11:13

wastl

1,884424

Stax, 12 10 bytes

Ã¢Â•Â¢ÃƒÂªv^Ã¢ÂŒÂÃƒÂ¶Ã¢Â–ÂºÃ¢Â™Â£ÃƒÂ„Ã‚Â»

Run and debug it

edited Aug 6 at 11:27

answered Aug 6 at 11:13

wastl

1,884424

edited Aug 6 at 11:27

answered Aug 6 at 11:13

wastl

1,884424

answered Aug 6 at 11:13

wastl

1,884424

answered Aug 6 at 11:13

wastl

1,884424

add a commentÂ |Â

up vote
4
down vote

Python 3, 77 72 bytes

f=lambda k,*l,m=:l and f(*l,m=m+[k*x for x in l])or max(m,key=m.count)

Try it online!

edited Aug 6 at 12:42

answered Aug 6 at 11:53

ovs

16.6k2956

add a commentÂ |Â

up vote
4
down vote

Python 3, 77 72 bytes

f=lambda k,*l,m=:l and f(*l,m=m+[k*x for x in l])or max(m,key=m.count)

Try it online!

edited Aug 6 at 12:42

answered Aug 6 at 11:53

ovs

16.6k2956

add a commentÂ |Â

up vote
4
down vote

Python 3, 77 72 bytes

f=lambda k,*l,m=:l and f(*l,m=m+[k*x for x in l])or max(m,key=m.count)

Try it online!

edited Aug 6 at 12:42

answered Aug 6 at 11:53

ovs

16.6k2956

Python 3, 77 72 bytes

f=lambda k,*l,m=:l and f(*l,m=m+[k*x for x in l])or max(m,key=m.count)

Try it online!

edited Aug 6 at 12:42

answered Aug 6 at 11:53

ovs

16.6k2956

edited Aug 6 at 12:42

answered Aug 6 at 11:53

ovs

16.6k2956

answered Aug 6 at 11:53

ovs

16.6k2956

answered Aug 6 at 11:53

ovs

16.6k2956

add a commentÂ |Â

up vote
4
down vote

JavaScript (ES6), 72 70 bytes

a=>a.map(m=o=(y,Y)=>a.map(x=>Y--<0?m=(o[x*=y]=-~o[x])<m?m:o[r=x]:0))|r

Try it online!

edited Aug 6 at 23:13

answered Aug 6 at 11:18

Arnauld

61.6k575258

add a commentÂ |Â

up vote
4
down vote

JavaScript (ES6), 72 70 bytes

a=>a.map(m=o=(y,Y)=>a.map(x=>Y--<0?m=(o[x*=y]=-~o[x])<m?m:o[r=x]:0))|r

Try it online!

edited Aug 6 at 23:13

answered Aug 6 at 11:18

Arnauld

61.6k575258

add a commentÂ |Â

up vote
4
down vote

JavaScript (ES6), 72 70 bytes

a=>a.map(m=o=(y,Y)=>a.map(x=>Y--<0?m=(o[x*=y]=-~o[x])<m?m:o[r=x]:0))|r

Try it online!

edited Aug 6 at 23:13

answered Aug 6 at 11:18

Arnauld

61.6k575258

JavaScript (ES6), 72 70 bytes

a=>a.map(m=o=(y,Y)=>a.map(x=>Y--<0?m=(o[x*=y]=-~o[x])<m?m:o[r=x]:0))|r

Try it online!

edited Aug 6 at 23:13

answered Aug 6 at 11:18

Arnauld

61.6k575258

edited Aug 6 at 23:13

answered Aug 6 at 11:18

Arnauld

61.6k575258

answered Aug 6 at 11:18

Arnauld

61.6k575258

answered Aug 6 at 11:18

Arnauld

61.6k575258

add a commentÂ |Â

up vote
3
down vote

Charcoal, 24 bytes

Ã¯Â¼Â·ÃŽÂ¸Ã¯Â¼Â¦ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸Ã¢ÂŠÂžÃÂ…ÃŽÂºÃ¯Â¼Â©Ã¢ÂŠÂŸÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Try it online! Link is to verbose version of code. Explanation:

Ã¯Â¼Â·ÃŽÂ¸

While the input array is non-empty...

ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸

... pop the last element and multiply the rest of the array by that element...

Ã¯Â¼Â¦...Ã¢ÂŠÂžÃÂ…ÃŽÂº

... and push the results to the predefined empty list.

Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Count the number of times each product appears in the list and take the maximum...

ÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹...

... then filter for the products whose count equals that maximum...

Ã¯Â¼Â©Ã¢ÂŠÂŸ

...then pop the last element and cast to string for implicit print.

answered Aug 6 at 13:41

Neil

74k743169

add a commentÂ |Â

up vote
3
down vote

Charcoal, 24 bytes

Ã¯Â¼Â·ÃŽÂ¸Ã¯Â¼Â¦ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸Ã¢ÂŠÂžÃÂ…ÃŽÂºÃ¯Â¼Â©Ã¢ÂŠÂŸÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Try it online! Link is to verbose version of code. Explanation:

Ã¯Â¼Â·ÃŽÂ¸

While the input array is non-empty...

ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸

... pop the last element and multiply the rest of the array by that element...

Ã¯Â¼Â¦...Ã¢ÂŠÂžÃÂ…ÃŽÂº

... and push the results to the predefined empty list.

Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Count the number of times each product appears in the list and take the maximum...

ÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹...

... then filter for the products whose count equals that maximum...

Ã¯Â¼Â©Ã¢ÂŠÂŸ

...then pop the last element and cast to string for implicit print.

answered Aug 6 at 13:41

Neil

74k743169

add a commentÂ |Â

up vote
3
down vote

Charcoal, 24 bytes

Ã¯Â¼Â·ÃŽÂ¸Ã¯Â¼Â¦ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸Ã¢ÂŠÂžÃÂ…ÃŽÂºÃ¯Â¼Â©Ã¢ÂŠÂŸÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Try it online! Link is to verbose version of code. Explanation:

Ã¯Â¼Â·ÃŽÂ¸

While the input array is non-empty...

ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸

... pop the last element and multiply the rest of the array by that element...

Ã¯Â¼Â¦...Ã¢ÂŠÂžÃÂ…ÃŽÂº

... and push the results to the predefined empty list.

Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Count the number of times each product appears in the list and take the maximum...

ÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹...

... then filter for the products whose count equals that maximum...

Ã¯Â¼Â©Ã¢ÂŠÂŸ

...then pop the last element and cast to string for implicit print.

answered Aug 6 at 13:41

Neil

74k743169

Charcoal, 24 bytes

Ã¯Â¼Â·ÃŽÂ¸Ã¯Â¼Â¦ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸Ã¢ÂŠÂžÃÂ…ÃŽÂºÃ¯Â¼Â©Ã¢ÂŠÂŸÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Try it online! Link is to verbose version of code. Explanation:

Ã¯Â¼Â·ÃŽÂ¸

While the input array is non-empty...

ÃƒÂ—Ã¢ÂŠÂŸÃŽÂ¸ÃŽÂ¸

... pop the last element and multiply the rest of the array by that element...

Ã¯Â¼Â¦...Ã¢ÂŠÂžÃÂ…ÃŽÂº

... and push the results to the predefined empty list.

Ã¢ÂŒÂˆÃ¯Â¼Â¥ÃÂ…Ã¢Â„Â–ÃÂ…ÃŽÂ»

Count the number of times each product appears in the list and take the maximum...

ÃŽÂ¦ÃÂ…Ã¢ÂÂ¼Ã¢Â„Â–ÃÂ…ÃŽÂ¹...

... then filter for the products whose count equals that maximum...

Ã¯Â¼Â©Ã¢ÂŠÂŸ

...then pop the last element and cast to string for implicit print.

answered Aug 6 at 13:41

Neil

74k743169

answered Aug 6 at 13:41

Neil

74k743169

answered Aug 6 at 13:41

Neil

74k743169

answered Aug 6 at 13:41

Neil

74k743169

add a commentÂ |Â

up vote
3
down vote

Attache, 59 bytes

Last##~SortBy#`&&:`~##Flat[UpperTriangle&1!Table&_!`*]^^0

Try it online!

Still working on golfing this down a bit, but I think this is near optimal for the approach I've chosen.

Explanation

This is a composition of three functions:

Flat[UpperTriangle&1!Table&_!`*]^^0

SortBy#`&&:`~

Last

The first function does the bulk of the computation:

Flat[UpperTriangle&1!Table&_!`*]^^0
 anonymous lambda; input: _ (e.g.: [2,3,4,5,6])
 Table&_!`* shorthand for Table[`*, _]
 this creates a multiplication table using the input
 e.g.:
 4 6 8 10 12
 6 9 12 15 18
 8 12 16 20 24
 10 15 20 25 30
 12 18 24 30 36

 UpperTriangle&1! takes the strict upper triangle of this matrix
 e.g.:
 0 6 8 10 12
 0 0 12 15 18
 0 0 0 20 24
 0 0 0 0 30
 0 0 0 0 0
Flat[ ]^^0 flattens this list and removes all 0s
 e.g.: [6, 8, 10, 12, 12, 15, 18, 20, 24, 30]

( ~SortBy ) # (`& &: `~)

f&:n <=> $ f[n, x] 
 <=> $ (`&)[`~, x] 
 <=> $ `~ & x

Going back to SortBy, this each element in the array by the number of times it appears in it.

Finally, Last takes the element which occurs the most. Ties are broken by the sorting algorithm.

answered Aug 6 at 18:24

Conor O'Brien

27.9k262156

Is the UpperTriangle part required? Can you just flatten the table and sort?
â€“Â svavil
Aug 7 at 12:14

@svavil Yes, it is required; [5, 2, 9, 10, 3, 4, 4, 4, 7] -> 16 instead of 20 without it.
â€“Â Conor O'Brien
Aug 7 at 18:41

add a commentÂ |Â

up vote
3
down vote

Attache, 59 bytes

Last##~SortBy#`&&:`~##Flat[UpperTriangle&1!Table&_!`*]^^0

Try it online!

Still working on golfing this down a bit, but I think this is near optimal for the approach I've chosen.

Explanation

This is a composition of three functions:

Flat[UpperTriangle&1!Table&_!`*]^^0

SortBy#`&&:`~

Last

The first function does the bulk of the computation:

Flat[UpperTriangle&1!Table&_!`*]^^0
 anonymous lambda; input: _ (e.g.: [2,3,4,5,6])
 Table&_!`* shorthand for Table[`*, _]
 this creates a multiplication table using the input
 e.g.:
 4 6 8 10 12
 6 9 12 15 18
 8 12 16 20 24
 10 15 20 25 30
 12 18 24 30 36

 UpperTriangle&1! takes the strict upper triangle of this matrix
 e.g.:
 0 6 8 10 12
 0 0 12 15 18
 0 0 0 20 24
 0 0 0 0 30
 0 0 0 0 0
Flat[ ]^^0 flattens this list and removes all 0s
 e.g.: [6, 8, 10, 12, 12, 15, 18, 20, 24, 30]

( ~SortBy ) # (`& &: `~)

f&:n <=> $ f[n, x] 
 <=> $ (`&)[`~, x] 
 <=> $ `~ & x

Going back to SortBy, this each element in the array by the number of times it appears in it.

Finally, Last takes the element which occurs the most. Ties are broken by the sorting algorithm.

answered Aug 6 at 18:24

Conor O'Brien

27.9k262156

Is the UpperTriangle part required? Can you just flatten the table and sort?
â€“Â svavil
Aug 7 at 12:14

@svavil Yes, it is required; [5, 2, 9, 10, 3, 4, 4, 4, 7] -> 16 instead of 20 without it.
â€“Â Conor O'Brien
Aug 7 at 18:41

add a commentÂ |Â

up vote
3
down vote

Attache, 59 bytes

Last##~SortBy#`&&:`~##Flat[UpperTriangle&1!Table&_!`*]^^0

Try it online!

Still working on golfing this down a bit, but I think this is near optimal for the approach I've chosen.

Explanation

This is a composition of three functions:

Flat[UpperTriangle&1!Table&_!`*]^^0

SortBy#`&&:`~

Last

The first function does the bulk of the computation:

Flat[UpperTriangle&1!Table&_!`*]^^0
 anonymous lambda; input: _ (e.g.: [2,3,4,5,6])
 Table&_!`* shorthand for Table[`*, _]
 this creates a multiplication table using the input
 e.g.:
 4 6 8 10 12
 6 9 12 15 18
 8 12 16 20 24
 10 15 20 25 30
 12 18 24 30 36

 UpperTriangle&1! takes the strict upper triangle of this matrix
 e.g.:
 0 6 8 10 12
 0 0 12 15 18
 0 0 0 20 24
 0 0 0 0 30
 0 0 0 0 0
Flat[ ]^^0 flattens this list and removes all 0s
 e.g.: [6, 8, 10, 12, 12, 15, 18, 20, 24, 30]

( ~SortBy ) # (`& &: `~)

f&:n <=> $ f[n, x] 
 <=> $ (`&)[`~, x] 
 <=> $ `~ & x

Going back to SortBy, this each element in the array by the number of times it appears in it.

Finally, Last takes the element which occurs the most. Ties are broken by the sorting algorithm.

answered Aug 6 at 18:24

Conor O'Brien

27.9k262156

Attache, 59 bytes

Last##~SortBy#`&&:`~##Flat[UpperTriangle&1!Table&_!`*]^^0

Try it online!

Still working on golfing this down a bit, but I think this is near optimal for the approach I've chosen.

Explanation

This is a composition of three functions:

Flat[UpperTriangle&1!Table&_!`*]^^0

SortBy#`&&:`~

Last

The first function does the bulk of the computation:

Flat[UpperTriangle&1!Table&_!`*]^^0
 anonymous lambda; input: _ (e.g.: [2,3,4,5,6])
 Table&_!`* shorthand for Table[`*, _]
 this creates a multiplication table using the input
 e.g.:
 4 6 8 10 12
 6 9 12 15 18
 8 12 16 20 24
 10 15 20 25 30
 12 18 24 30 36

 UpperTriangle&1! takes the strict upper triangle of this matrix
 e.g.:
 0 6 8 10 12
 0 0 12 15 18
 0 0 0 20 24
 0 0 0 0 30
 0 0 0 0 0
Flat[ ]^^0 flattens this list and removes all 0s
 e.g.: [6, 8, 10, 12, 12, 15, 18, 20, 24, 30]

( ~SortBy ) # (`& &: `~)

f&:n <=> $ f[n, x] 
 <=> $ (`&)[`~, x] 
 <=> $ `~ & x

Going back to SortBy, this each element in the array by the number of times it appears in it.

Finally, Last takes the element which occurs the most. Ties are broken by the sorting algorithm.

answered Aug 6 at 18:24

Conor O'Brien

27.9k262156

answered Aug 6 at 18:24

Conor O'Brien

27.9k262156

answered Aug 6 at 18:24

Conor O'Brien

27.9k262156

answered Aug 6 at 18:24

Conor O'Brien

27.9k262156

Is the UpperTriangle part required? Can you just flatten the table and sort?
â€“Â svavil
Aug 7 at 12:14

@svavil Yes, it is required; [5, 2, 9, 10, 3, 4, 4, 4, 7] -> 16 instead of 20 without it.
â€“Â Conor O'Brien
Aug 7 at 18:41

add a commentÂ |Â

Is the UpperTriangle part required? Can you just flatten the table and sort?
â€“Â svavil
Aug 7 at 12:14

@svavil Yes, it is required; [5, 2, 9, 10, 3, 4, 4, 4, 7] -> 16 instead of 20 without it.
â€“Â Conor O'Brien
Aug 7 at 18:41

Is the UpperTriangle part required? Can you just flatten the table and sort?
â€“Â svavil
Aug 7 at 12:14

@svavil Yes, it is required; [5, 2, 9, 10, 3, 4, 4, 4, 7] -> 16 instead of 20 without it.
â€“Â Conor O'Brien
Aug 7 at 18:41

add a commentÂ |Â

up vote
3
down vote

APL (Dyalog Unicode), 29 27 19 bytes

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚

Try it online!

Tacit fn.

Thanks to AdÃƒÂ¡m for the tacit version and 2 bytes.

Thanks to ngn for 8 bytes!

How:

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚
 Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚ Ã¢ÂÂ Multiply each element with the entire argument, then
 Ã¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨ Ã¢ÂÂ Remove 1 from the first, two from the next etc. (removes repeated multiplications);
 Ã¢ÂÂ The result is then fed into the function:
 Ã¢ÂˆÂŠÃ¢ÂÂµ Ã¢ÂÂ Flatten the result;
 Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸ Ã¢ÂÂ Key; creates a matrix in which each row corresponds to a unique product;
 Ã¢ÂŠÂ¢/ Ã¢ÂÂ Get the rightmost column of the matrix;
 Ã¢ÂŒÂˆ/ Ã¢ÂÂ Get the highest value.

edited Aug 7 at 18:23

answered Aug 7 at 14:48

J. SallÃ©

1,298218

1

This is only 27.
â€“Â AdÃ¡m
Aug 7 at 15:18

add a commentÂ |Â

up vote
3
down vote

APL (Dyalog Unicode), 29 27 19 bytes

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚

Try it online!

Tacit fn.

Thanks to AdÃƒÂ¡m for the tacit version and 2 bytes.

Thanks to ngn for 8 bytes!

How:

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚
 Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚ Ã¢ÂÂ Multiply each element with the entire argument, then
 Ã¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨ Ã¢ÂÂ Remove 1 from the first, two from the next etc. (removes repeated multiplications);
 Ã¢ÂÂ The result is then fed into the function:
 Ã¢ÂˆÂŠÃ¢ÂÂµ Ã¢ÂÂ Flatten the result;
 Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸ Ã¢ÂÂ Key; creates a matrix in which each row corresponds to a unique product;
 Ã¢ÂŠÂ¢/ Ã¢ÂÂ Get the rightmost column of the matrix;
 Ã¢ÂŒÂˆ/ Ã¢ÂÂ Get the highest value.

edited Aug 7 at 18:23

answered Aug 7 at 14:48

J. SallÃ©

1,298218

1

This is only 27.
â€“Â AdÃ¡m
Aug 7 at 15:18

add a commentÂ |Â

up vote
3
down vote

APL (Dyalog Unicode), 29 27 19 bytes

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚

Try it online!

Tacit fn.

Thanks to AdÃƒÂ¡m for the tacit version and 2 bytes.

Thanks to ngn for 8 bytes!

How:

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚
 Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚ Ã¢ÂÂ Multiply each element with the entire argument, then
 Ã¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨ Ã¢ÂÂ Remove 1 from the first, two from the next etc. (removes repeated multiplications);
 Ã¢ÂÂ The result is then fed into the function:
 Ã¢ÂˆÂŠÃ¢ÂÂµ Ã¢ÂÂ Flatten the result;
 Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸ Ã¢ÂÂ Key; creates a matrix in which each row corresponds to a unique product;
 Ã¢ÂŠÂ¢/ Ã¢ÂÂ Get the rightmost column of the matrix;
 Ã¢ÂŒÂˆ/ Ã¢ÂÂ Get the highest value.

edited Aug 7 at 18:23

answered Aug 7 at 14:48

J. SallÃ©

1,298218

APL (Dyalog Unicode), 29 27 19 bytes

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚

Try it online!

Tacit fn.

Thanks to AdÃƒÂ¡m for the tacit version and 2 bytes.

Thanks to ngn for 8 bytes!

How:

Ã¢ÂŒÂˆ/Ã¢ÂŠÂ¢/Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸Ã¢ÂˆÂŠÃ¢ÂÂµÃ¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚
 Ã¢ÂŠÂ¢ÃƒÂ—Ã¢ÂŠÂ‚ Ã¢ÂÂ Multiply each element with the entire argument, then
 Ã¢ÂÂ³Ã¢ÂˆÂ˜Ã¢Â‰Â¢Ã¢Â†Â“Ã‚Â¨ Ã¢ÂÂ Remove 1 from the first, two from the next etc. (removes repeated multiplications);
 Ã¢ÂÂ The result is then fed into the function:
 Ã¢ÂˆÂŠÃ¢ÂÂµ Ã¢ÂÂ Flatten the result;
 Ã¢ÂŠÂ£Ã‚Â¨Ã¢ÂŒÂ¸ Ã¢ÂÂ Key; creates a matrix in which each row corresponds to a unique product;
 Ã¢ÂŠÂ¢/ Ã¢ÂÂ Get the rightmost column of the matrix;
 Ã¢ÂŒÂˆ/ Ã¢ÂÂ Get the highest value.

edited Aug 7 at 18:23

answered Aug 7 at 14:48

J. SallÃ©

1,298218

edited Aug 7 at 18:23

answered Aug 7 at 14:48

J. SallÃ©

1,298218

answered Aug 7 at 14:48

J. SallÃ©

1,298218

answered Aug 7 at 14:48

J. SallÃ©

1,298218

1

This is only 27.
â€“Â AdÃ¡m
Aug 7 at 15:18

add a commentÂ |Â

1

This is only 27.
â€“Â AdÃ¡m
Aug 7 at 15:18

This is only 27.
â€“Â AdÃ¡m
Aug 7 at 15:18

add a commentÂ |Â

up vote
3
down vote

CJam, 70 68 bytes

q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

Try it online!

Explanation

q',/S*~ Turn input string into a valid CJam array
 _,( Find the length of the array and subtract 1
 :L Assign the result to L
 fX Outer for loop
 LX-,0a+[X1++*](; Create an array with all the array indexes bigger than X
 fY Inner for loop
 _X=_Y=@* Create a multiple of array[X] and array[Y] (Guaranteed to be from a unique combination of factors)
 ~;] Casts away all stack items except for an array of the multiples
 __@e=$; Sorts array by number of occurrences (largest number of occurences at the end)
 _,(= Gets the last element of the array

You will need to scroll right to see the explanations as the code is quite long, as well as the explanations.

This should be golfable, considering I'm terrible at CJam.

Changes:

Helen cut off 2 bytes!

Old: q',/S*~_,1-:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,1-=

New: q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

By changing the 1-s to simply ( we get the same effect but with a lower byte count.

edited Aug 8 at 18:37

answered Aug 7 at 23:21

Helen

1055

add a commentÂ |Â

up vote
3
down vote

CJam, 70 68 bytes

q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

Try it online!

Explanation

q',/S*~ Turn input string into a valid CJam array
 _,( Find the length of the array and subtract 1
 :L Assign the result to L
 fX Outer for loop
 LX-,0a+[X1++*](; Create an array with all the array indexes bigger than X
 fY Inner for loop
 _X=_Y=@* Create a multiple of array[X] and array[Y] (Guaranteed to be from a unique combination of factors)
 ~;] Casts away all stack items except for an array of the multiples
 __@e=$; Sorts array by number of occurrences (largest number of occurences at the end)
 _,(= Gets the last element of the array

You will need to scroll right to see the explanations as the code is quite long, as well as the explanations.

This should be golfable, considering I'm terrible at CJam.

Changes:

Helen cut off 2 bytes!

Old: q',/S*~_,1-:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,1-=

New: q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

By changing the 1-s to simply ( we get the same effect but with a lower byte count.

edited Aug 8 at 18:37

answered Aug 7 at 23:21

Helen

1055

add a commentÂ |Â

up vote
3
down vote

CJam, 70 68 bytes

q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

Try it online!

Explanation

q',/S*~ Turn input string into a valid CJam array
 _,( Find the length of the array and subtract 1
 :L Assign the result to L
 fX Outer for loop
 LX-,0a+[X1++*](; Create an array with all the array indexes bigger than X
 fY Inner for loop
 _X=_Y=@* Create a multiple of array[X] and array[Y] (Guaranteed to be from a unique combination of factors)
 ~;] Casts away all stack items except for an array of the multiples
 __@e=$; Sorts array by number of occurrences (largest number of occurences at the end)
 _,(= Gets the last element of the array

You will need to scroll right to see the explanations as the code is quite long, as well as the explanations.

This should be golfable, considering I'm terrible at CJam.

Changes:

Helen cut off 2 bytes!

Old: q',/S*~_,1-:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,1-=

New: q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

By changing the 1-s to simply ( we get the same effect but with a lower byte count.

edited Aug 8 at 18:37

answered Aug 7 at 23:21

Helen

1055

CJam, 70 68 bytes

q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

Try it online!

Explanation

q',/S*~ Turn input string into a valid CJam array
 _,( Find the length of the array and subtract 1
 :L Assign the result to L
 fX Outer for loop
 LX-,0a+[X1++*](; Create an array with all the array indexes bigger than X
 fY Inner for loop
 _X=_Y=@* Create a multiple of array[X] and array[Y] (Guaranteed to be from a unique combination of factors)
 ~;] Casts away all stack items except for an array of the multiples
 __@e=$; Sorts array by number of occurrences (largest number of occurences at the end)
 _,(= Gets the last element of the array

You will need to scroll right to see the explanations as the code is quite long, as well as the explanations.

This should be golfable, considering I'm terrible at CJam.

Changes:

Helen cut off 2 bytes!

Old: q',/S*~_,1-:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,1-=

New: q',/S*~_,(:LLX-,0a+[X1++*](;_X=_Y=@*fYfX]~;]__@e=$;_,(=

By changing the 1-s to simply ( we get the same effect but with a lower byte count.

edited Aug 8 at 18:37

answered Aug 7 at 23:21

Helen

1055

edited Aug 8 at 18:37

answered Aug 7 at 23:21

Helen

1055

answered Aug 7 at 23:21

Helen

1055

answered Aug 7 at 23:21

Helen

1055

add a commentÂ |Â

up vote
2
down vote

Java (JDK 10), 132 bytes

a->int l=a.length,i=l,j=0,r=99999,m=new int[r];for(;i-->0;)for(j=l;--j>i;)m[a[i]*a[j]]++;for(;r-->0;)i=m[r]<i?i:m[j=r];return j;

Try it online!

answered Aug 7 at 8:35

7,37311739

add a commentÂ |Â

up vote
2
down vote

Java (JDK 10), 132 bytes

a->int l=a.length,i=l,j=0,r=99999,m=new int[r];for(;i-->0;)for(j=l;--j>i;)m[a[i]*a[j]]++;for(;r-->0;)i=m[r]<i?i:m[j=r];return j;

Try it online!

answered Aug 7 at 8:35

7,37311739

add a commentÂ |Â

up vote
2
down vote

Java (JDK 10), 132 bytes

a->int l=a.length,i=l,j=0,r=99999,m=new int[r];for(;i-->0;)for(j=l;--j>i;)m[a[i]*a[j]]++;for(;r-->0;)i=m[r]<i?i:m[j=r];return j;

Try it online!

answered Aug 7 at 8:35

7,37311739

Java (JDK 10), 132 bytes

a->int l=a.length,i=l,j=0,r=99999,m=new int[r];for(;i-->0;)for(j=l;--j>i;)m[a[i]*a[j]]++;for(;r-->0;)i=m[r]<i?i:m[j=r];return j;

Try it online!

answered Aug 7 at 8:35

7,37311739

answered Aug 7 at 8:35

7,37311739

answered Aug 7 at 8:35

7,37311739

answered Aug 7 at 8:35

7,37311739

add a commentÂ |Â

up vote
2
down vote

Japt `-h`, 20 bytes

Not the best. I dont know how to make this code shorter

Ã‚Â£UsYÃƒÂ„ Ã‚Â®*X
c n ÃƒÂ³Ã‚Â¥ ÃƒÂ±ÃƒÂŠo

Try it online!

answered Aug 7 at 15:12

Luis felipe De jesus Munoz

2,4451039

add a commentÂ |Â

up vote
2
down vote

Japt `-h`, 20 bytes

Not the best. I dont know how to make this code shorter

Ã‚Â£UsYÃƒÂ„ Ã‚Â®*X
c n ÃƒÂ³Ã‚Â¥ ÃƒÂ±ÃƒÂŠo

Try it online!

answered Aug 7 at 15:12

Luis felipe De jesus Munoz

2,4451039

add a commentÂ |Â

up vote
2
down vote

Japt `-h`, 20 bytes

Not the best. I dont know how to make this code shorter

Ã‚Â£UsYÃƒÂ„ Ã‚Â®*X
c n ÃƒÂ³Ã‚Â¥ ÃƒÂ±ÃƒÂŠo

Try it online!

answered Aug 7 at 15:12

Luis felipe De jesus Munoz

2,4451039

Japt `-h`, 20 bytes

Not the best. I dont know how to make this code shorter

Ã‚Â£UsYÃƒÂ„ Ã‚Â®*X
c n ÃƒÂ³Ã‚Â¥ ÃƒÂ±ÃƒÂŠo

Try it online!

answered Aug 7 at 15:12

Luis felipe De jesus Munoz

2,4451039

answered Aug 7 at 15:12

Luis felipe De jesus Munoz

2,4451039

answered Aug 7 at 15:12

Luis felipe De jesus Munoz

2,4451039

answered Aug 7 at 15:12

Luis felipe De jesus Munoz

2,4451039

add a commentÂ |Â

up vote
2
down vote

Husk, 7 bytes

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2

Try it online!

Explanation

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2 -- example input [3,3,3]
 Ã¡Â¹Â–2 -- subsequences of length 2: [[3,3],[3,3],[3,3]]
 mÃŽÂ  -- map product: [9,9,9]
Ã¡Â¹Â  -- apply 
 # -- | count occurences in list
 Ã¢Â–Âº -- to maxOn that list: [9]

answered Aug 7 at 15:34

BWO

9,06111569

add a commentÂ |Â

up vote
2
down vote

Husk, 7 bytes

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2

Try it online!

Explanation

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2 -- example input [3,3,3]
 Ã¡Â¹Â–2 -- subsequences of length 2: [[3,3],[3,3],[3,3]]
 mÃŽÂ  -- map product: [9,9,9]
Ã¡Â¹Â  -- apply 
 # -- | count occurences in list
 Ã¢Â–Âº -- to maxOn that list: [9]

answered Aug 7 at 15:34

BWO

9,06111569

add a commentÂ |Â

up vote
2
down vote

Husk, 7 bytes

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2

Try it online!

Explanation

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2 -- example input [3,3,3]
 Ã¡Â¹Â–2 -- subsequences of length 2: [[3,3],[3,3],[3,3]]
 mÃŽÂ  -- map product: [9,9,9]
Ã¡Â¹Â  -- apply 
 # -- | count occurences in list
 Ã¢Â–Âº -- to maxOn that list: [9]

answered Aug 7 at 15:34

BWO

9,06111569

Husk, 7 bytes

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2

Try it online!

Explanation

Ã¡Â¹Â Ã¢Â–Âº#mÃŽÂ Ã¡Â¹Â–2 -- example input [3,3,3]
 Ã¡Â¹Â–2 -- subsequences of length 2: [[3,3],[3,3],[3,3]]
 mÃŽÂ  -- map product: [9,9,9]
Ã¡Â¹Â  -- apply 
 # -- | count occurences in list
 Ã¢Â–Âº -- to maxOn that list: [9]

answered Aug 7 at 15:34

BWO

9,06111569

answered Aug 7 at 15:34

BWO

9,06111569

answered Aug 7 at 15:34

BWO

9,06111569

answered Aug 7 at 15:34

BWO

9,06111569

add a commentÂ |Â

up vote
2
down vote

Haskell, 96 94 bytes

^{-2 bytes thanks to nimi (using sortOn(0<$) instead of length)!}

import Data.List
f a|b<-zip[0..]a=last.last.sortOn(0<$).group$sort[x*y|(i,x)<-b,(j,y)<-b,i/=j]

Try it online!

edited Aug 7 at 19:29

answered Aug 7 at 15:50

BWO

9,06111569

1

sortOn(0<$).
â€“Â nimi
Aug 7 at 19:26

add a commentÂ |Â

up vote
2
down vote

Haskell, 96 94 bytes

^{-2 bytes thanks to nimi (using sortOn(0<$) instead of length)!}

import Data.List
f a|b<-zip[0..]a=last.last.sortOn(0<$).group$sort[x*y|(i,x)<-b,(j,y)<-b,i/=j]

Try it online!

edited Aug 7 at 19:29

answered Aug 7 at 15:50

BWO

9,06111569

1

sortOn(0<$).
â€“Â nimi
Aug 7 at 19:26

add a commentÂ |Â

up vote
2
down vote

Haskell, 96 94 bytes

^{-2 bytes thanks to nimi (using sortOn(0<$) instead of length)!}

import Data.List
f a|b<-zip[0..]a=last.last.sortOn(0<$).group$sort[x*y|(i,x)<-b,(j,y)<-b,i/=j]

Try it online!

edited Aug 7 at 19:29

answered Aug 7 at 15:50

BWO

9,06111569

Haskell, 96 94 bytes

^{-2 bytes thanks to nimi (using sortOn(0<$) instead of length)!}

import Data.List
f a|b<-zip[0..]a=last.last.sortOn(0<$).group$sort[x*y|(i,x)<-b,(j,y)<-b,i/=j]

Try it online!

edited Aug 7 at 19:29

answered Aug 7 at 15:50

BWO

9,06111569

edited Aug 7 at 19:29

answered Aug 7 at 15:50

BWO

9,06111569

answered Aug 7 at 15:50

BWO

9,06111569

answered Aug 7 at 15:50

BWO

9,06111569

1

sortOn(0<$).
â€“Â nimi
Aug 7 at 19:26

add a commentÂ |Â

1

sortOn(0<$).
â€“Â nimi
Aug 7 at 19:26

sortOn(0<$).
â€“Â nimi
Aug 7 at 19:26

add a commentÂ |Â

up vote
2
down vote

MATLAB 39 bytes

a=input('');
b=triu(a'*a,1);
mode(b(b~=0))

Also check out answer by Jacob Watson

edited Aug 8 at 14:48

answered Aug 8 at 0:40

aaaaaa

2816

1

Having the second line be b=triu(a'*a,1); saves 4 bytes.
â€“Â sundar
Aug 8 at 12:32

@sundar Oh snap, you are right :) I had triu intially but drifted away somehow
â€“Â aaaaaa
Aug 8 at 14:47

Good solution, I didn't realise the upper triangle function was so short!
â€“Â Jacob Watson
Aug 10 at 8:19

add a commentÂ |Â

up vote
2
down vote

MATLAB 39 bytes

a=input('');
b=triu(a'*a,1);
mode(b(b~=0))

Also check out answer by Jacob Watson

edited Aug 8 at 14:48

answered Aug 8 at 0:40

aaaaaa

2816

1

Having the second line be b=triu(a'*a,1); saves 4 bytes.
â€“Â sundar
Aug 8 at 12:32

@sundar Oh snap, you are right :) I had triu intially but drifted away somehow
â€“Â aaaaaa
Aug 8 at 14:47

Good solution, I didn't realise the upper triangle function was so short!
â€“Â Jacob Watson
Aug 10 at 8:19

add a commentÂ |Â

up vote
2
down vote

MATLAB 39 bytes

a=input('');
b=triu(a'*a,1);
mode(b(b~=0))

Also check out answer by Jacob Watson

edited Aug 8 at 14:48

answered Aug 8 at 0:40

aaaaaa

2816

MATLAB 39 bytes

a=input('');
b=triu(a'*a,1);
mode(b(b~=0))

Also check out answer by Jacob Watson

edited Aug 8 at 14:48

answered Aug 8 at 0:40

aaaaaa

2816

edited Aug 8 at 14:48

answered Aug 8 at 0:40

aaaaaa

2816

answered Aug 8 at 0:40

aaaaaa

2816

answered Aug 8 at 0:40

aaaaaa

2816

1

Having the second line be b=triu(a'*a,1); saves 4 bytes.
â€“Â sundar
Aug 8 at 12:32

@sundar Oh snap, you are right :) I had triu intially but drifted away somehow
â€“Â aaaaaa
Aug 8 at 14:47

Good solution, I didn't realise the upper triangle function was so short!
â€“Â Jacob Watson
Aug 10 at 8:19

add a commentÂ |Â

1

Having the second line be b=triu(a'*a,1); saves 4 bytes.
â€“Â sundar
Aug 8 at 12:32

@sundar Oh snap, you are right :) I had triu intially but drifted away somehow
â€“Â aaaaaa
Aug 8 at 14:47

Good solution, I didn't realise the upper triangle function was so short!
â€“Â Jacob Watson
Aug 10 at 8:19

Having the second line be b=triu(a'*a,1); saves 4 bytes.
â€“Â sundar
Aug 8 at 12:32

@sundar Oh snap, you are right :) I had triu intially but drifted away somehow
â€“Â aaaaaa
Aug 8 at 14:47

Good solution, I didn't realise the upper triangle function was so short!
â€“Â Jacob Watson
Aug 10 at 8:19

add a commentÂ |Â

up vote
2
down vote

SQL Server, 93 bytes

SELECT TOP 1a.a*b.a
FROM @ a
JOIN @ b ON a.i<b.i
GROUP BY a.a*b.a
ORDER BY COUNT(a.a*b.a)DESC

Input is assumed to come from a table of the form

DECLARE @ TABLE (A int, i int identity);

Example table population:

INSERT INTO @ VALUES (9), (7), (10), (9), (7), (8), (5), (10), (1);

Explanation:

I assume a "list of integers" will have an index associated with them, which in my case is the column i. The column a contains the values of the list.

I create products of every pair, where the left pair comes in the list earlier than the right pair. I then group on the product, and sort by the most populous number.

I'm a little sad I didn't get to use any cte or partitioning clauses, but they were just too long. SELECT is a very expensive keyword.

Alternative, 183 bytes

WITH c
AS(SELECT a,ROW_NUMBER()OVER(ORDER BY a)r
FROM @),d AS(SELECT a.a*b.a p,COUNT(a.a*b.a)m
FROM c a
JOIN c b ON a.r<b.r GROUP BY a.a*b.a)SELECT TOP 1p
FROM d
ORDER BY m DESC

answered Aug 8 at 17:52

Brian J

653613

add a commentÂ |Â

up vote
2
down vote

SQL Server, 93 bytes

SELECT TOP 1a.a*b.a
FROM @ a
JOIN @ b ON a.i<b.i
GROUP BY a.a*b.a
ORDER BY COUNT(a.a*b.a)DESC

Input is assumed to come from a table of the form

DECLARE @ TABLE (A int, i int identity);

Example table population:

INSERT INTO @ VALUES (9), (7), (10), (9), (7), (8), (5), (10), (1);

Explanation:

I assume a "list of integers" will have an index associated with them, which in my case is the column i. The column a contains the values of the list.

I create products of every pair, where the left pair comes in the list earlier than the right pair. I then group on the product, and sort by the most populous number.

I'm a little sad I didn't get to use any cte or partitioning clauses, but they were just too long. SELECT is a very expensive keyword.

Alternative, 183 bytes

WITH c
AS(SELECT a,ROW_NUMBER()OVER(ORDER BY a)r
FROM @),d AS(SELECT a.a*b.a p,COUNT(a.a*b.a)m
FROM c a
JOIN c b ON a.r<b.r GROUP BY a.a*b.a)SELECT TOP 1p
FROM d
ORDER BY m DESC

answered Aug 8 at 17:52

Brian J

653613

add a commentÂ |Â

up vote
2
down vote

SQL Server, 93 bytes

SELECT TOP 1a.a*b.a
FROM @ a
JOIN @ b ON a.i<b.i
GROUP BY a.a*b.a
ORDER BY COUNT(a.a*b.a)DESC

Input is assumed to come from a table of the form

DECLARE @ TABLE (A int, i int identity);

Example table population:

INSERT INTO @ VALUES (9), (7), (10), (9), (7), (8), (5), (10), (1);

Explanation:

I assume a "list of integers" will have an index associated with them, which in my case is the column i. The column a contains the values of the list.

I create products of every pair, where the left pair comes in the list earlier than the right pair. I then group on the product, and sort by the most populous number.

I'm a little sad I didn't get to use any cte or partitioning clauses, but they were just too long. SELECT is a very expensive keyword.

Alternative, 183 bytes

WITH c
AS(SELECT a,ROW_NUMBER()OVER(ORDER BY a)r
FROM @),d AS(SELECT a.a*b.a p,COUNT(a.a*b.a)m
FROM c a
JOIN c b ON a.r<b.r GROUP BY a.a*b.a)SELECT TOP 1p
FROM d
ORDER BY m DESC

answered Aug 8 at 17:52

Brian J

653613

SQL Server, 93 bytes

SELECT TOP 1a.a*b.a
FROM @ a
JOIN @ b ON a.i<b.i
GROUP BY a.a*b.a
ORDER BY COUNT(a.a*b.a)DESC

Input is assumed to come from a table of the form

DECLARE @ TABLE (A int, i int identity);

Example table population:

INSERT INTO @ VALUES (9), (7), (10), (9), (7), (8), (5), (10), (1);

Explanation:

I assume a "list of integers" will have an index associated with them, which in my case is the column i. The column a contains the values of the list.

I create products of every pair, where the left pair comes in the list earlier than the right pair. I then group on the product, and sort by the most populous number.

I'm a little sad I didn't get to use any cte or partitioning clauses, but they were just too long. SELECT is a very expensive keyword.

Alternative, 183 bytes

WITH c
AS(SELECT a,ROW_NUMBER()OVER(ORDER BY a)r
FROM @),d AS(SELECT a.a*b.a p,COUNT(a.a*b.a)m
FROM c a
JOIN c b ON a.r<b.r GROUP BY a.a*b.a)SELECT TOP 1p
FROM d
ORDER BY m DESC

answered Aug 8 at 17:52

Brian J

653613

answered Aug 8 at 17:52

Brian J

653613

answered Aug 8 at 17:52

Brian J

653613

answered Aug 8 at 17:52

Brian J

653613

add a commentÂ |Â

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22 Answers 22

22 Answers 22

R, 54 50 41 bytes

R, 54 50 41 bytes

R, 54 50 41 bytes

R, 54 50 41 bytes

Brachylog, 11 bytes

Explanation

Brachylog, 11 bytes

Explanation

Brachylog, 11 bytes

Explanation

Brachylog, 11 bytes

Explanation

Pyth, 12 bytes

Pyth, 12 bytes

Pyth, 12 bytes

Pyth, 12 bytes

MATL, 8 7 bytes

8 bytes

MATL, 8 7 bytes

8 bytes

MATL, 8 7 bytes

8 bytes

MATL, 8 7 bytes

8 bytes

Mathematica, 32 bytes

Mathematica, 32 bytes

Mathematica, 32 bytes

Mathematica, 32 bytes

Jelly, 6 bytes

How it works

Jelly, 6 bytes

How it works

Jelly, 6 bytes

How it works

Jelly, 6 bytes

22 Answers
22

Japt `-h`, 20 bytes

22 Answers
22

22 Answers
22

Japt `-h`, 20 bytes

Japt `-h`, 20 bytes

Japt `-h`, 20 bytes

Japt `-h`, 20 bytes