Combinaison ruby Array multidimensionnel to get a Array two dimensional

Question

I have a Array multidimensionnel like:

[[1, 1, 4], [2],[2, 3]]

How to get a combinaison each element except the combinaison in the same array: [1, 1],[1, 4],[2, 3]

I want to get:

[1, 2],[1, 3],[4, 2],[4, 3],[2, 3]

Thanks.

why you have [2,3] at the end but you don't have [1,4] ? Did you try something? — radubogdan, Oct 23 '15 at 09:48
@radubogdan, presumably, `[a,b]` should be included if, for some `i` and `j`, `i — Cary Swoveland, Oct 23 '15 at 14:36
Doug, when you give an example it's helpful to assign each input object to a variable; for example, `arr = [[1,1,...]`. That way, readers can refer to `arr` in answers and comments without having to define it. — Cary Swoveland, Oct 23 '15 at 14:43
Shouldn't the array returned include `[2,2]`? If so, please edit; if not, please edit to explain why. — Cary Swoveland, Oct 23 '15 at 15:50

nsave · Accepted Answer · 2015-10-24T08:14:57.443

3

Short answer is:

[[1, 1, 4], [2],[2, 3]].combination(2).flat_map {|x,y| x.product(y)}.uniq
# => [[1, 2], [4, 2], [1, 3], [4, 3], [2, 2], [2, 3]]

Step by step

step1 = [[1, 1, 4], [2],[2, 3]].combination(2) 
# => [[[1, 1, 4], [2]], [[1, 1, 4], [2, 3]], [[2], [2, 3]]]

step2 = step1.flat_map {|x,y| x.product(y)}
# => [[1, 2], [1, 2], [4, 2], [1, 2], [1, 3], [1, 2], [1, 3], [4, 2], [4, 3], [2, 2], [2, 3]]

result = step2.uniq
# => [[1, 2], [4, 2], [1, 3], [4, 3], [2, 2], [2, 3]]

Update

For full uniqueness you could use:

[[1, 1, 4], [2],[2, 3, 4]].combination(2).flat_map {|x,y| x.product(y)}.map(&:sort).uniq

edited Oct 24 '15 at 08:14

answered Oct 23 '15 at 09:51

nsave

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if i have : [[1, 1, 4], [2],[2, 3, 4]].combination(2).map {|x,y| x.product(y)}.flatten(1).sort.uniq, i get [[1, 2], [1, 3], [1, 4], [2, 2], [2, 3], [2, 4], [4, 2], [4, 3], [4, 4]], so [2, 4] and [4, 2] is not uniq – Pf Dong Oct 23 '15 at 12:51
Check my update. Next time please describe what you want with all details – nsave Oct 23 '15 at 13:31
Thanks, I get it too. – Pf Dong Oct 23 '15 at 13:50

score 1 · Answer 2 · edited May 23 '17 at 11:52

arr = [[1, 1, 4], [2], [2, 3]]

a = arr.map(&:uniq)
(arr.size-1).times.flat_map { |i| arr[i].product(arr[i+1..-1].flatten.uniq)}.uniq
  #=> [[1,2],[1,3],[4,2],[4,3],[2,2],[2,3]]

Here's another way that uses the method Array#difference that I defined here:

arr.flatten.combination(2).to_a.difference(arr.flat_map { |a| a.combination(2).to_a }).uniq

Array#difference is similar to Array#-. The difference is illustrated in the following example:

a = [1,2,3,4,3,2,2,4]
b = [2,3,4,4,4]

a     -      b #=> [1]
a.difference b #=> [1, 3, 2, 2]

Combinaison ruby Array multidimensionnel to get a Array two dimensional

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