Creating pairs from an Array?

Question

Is there a simple way to create pairs from an array?

For example, if I have an array [1,2,3,4] how would I go about trying to return this array?

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

Every element is paired with every other other element except itself, and duplicates are allowed.

What you describe is not an array, not even a valid Ruby code. — sawa
– sawa, Commented Jan 16, 2013 at 17:46

BaronVonBraun · Accepted Answer · 2013-01-16 17:44:06Z

4

You can use Array#permutation for this:

[1,2,3,4].permutation(2).to_a
# => [[1, 2], [1, 3], [1, 4], [2, 1], [2, 3], [2, 4], [3, 1], [3, 2], [3, 4], [4, 1], [4, 2], [4, 3]]

answered Jan 16, 2013 at 17:44

BaronVonBraun

4,29125 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user1014888 Over a year ago

How can I access one of the elements in each of the pair, for example say I want to increment the second value in each pair by 1. e.g. [1,3],[1,4].....

Krule · Accepted Answer · 2013-01-16 17:59:57Z

2

[1,2,3,4].permutation(2).map{ |n| "(#{ n.join(",") })" }
# => ["(1,2)", "(1,3)", "(1,4)", "(2,1)", "(2,3)", "(2,4)", "(3,1)", "(3,2)", "(3,4)", "(4,1)", "(4,2)", "(4,3)"]

edited Jan 16, 2013 at 17:59

answered Jan 16, 2013 at 17:44

Krule

6,4963 gold badges36 silver badges56 bronze badges

Collectives™ on Stack Overflow

Creating pairs from an Array?

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related