CODEWITHSUNDEEP
ruby
user3060126
user3060126

Reputation: 501

How to combine 2 strings from an array without repeats in Ruby?

In Ruby, what's an elegant way to combine 2 strings from an array without repeating them? Example:

array = ['one', 'two', 'three', 'four']

And I want my output to be:

['onetwo', 'onethree', 'onefour', 'twothree', 'twofour', 'threefour']

Seems simple enough but I've been pretty stumped!

Edit: this is for doing something with anagrams so order does not matter. ('onetwo' ends up being equivalent to 'twoone'.)

Upvotes: 0

Views: 90

Answers (1)

Cary Swoveland
Cary Swoveland

Reputation: 110745

You can use Arrary#combination, Enumerable#map and Array#join for that.

Code

array.combination(2).map(&:join)
  #=> ["onetwo", "onethree", "onefour", "twothree", "twofour", "threefour"]

Explanation

array = ['one', 'two', 'three', 'four']

a = array.combination(2)
  #=> #<Enumerator: ["one", "two", "three", "four"]:combination(2)>

To view the contents of the enumerator:

a.to_a
  #=> [["one", "two"  ], ["one", "three"], ["one"  , "four"],
  #    ["two", "three"], ["two", "four" ], ["three", "four"]]

Then

a.map(&:join)

which has the same effect as:

a.map { |e| e.join }
  #=> ["onetwo", "onethree", "onefour", "twothree", "twofour", "threefour"]

If you wanted "twoone" as well as "onetwo", use Array#permutation instead of combination:

array.permutation(2).map(&:join)
  #=> ["onetwo"  , "onethree", "onefour"  , "twoone" , "twothree", "twofour",
  #    "threeone", "threetwo", "threefour", "fourone", "fourtwo" , "fourthree"]

Upvotes: 3

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