Extends Array by defining Array#riffle and Array.riffle to merge multiple arrays as if riffling a deck of cards.

Algorithm Description

riffle iterates over argument arrays and selects a random number of items from each to remove from the front (this default subsequence length, or group size is in (1..3)). The removed items are then appended to a new array which is returned as the result after all items from each argument array have been merged. This iteration continues until all argument arrays are empty and all items have been merged.

The order of items in each argument array is preserved in the resulting array relative to other items originating from the same argument array.

numbers = [1, 2, 3, 4, 5, 6]
letters = %w(a b c d e f)

numbers.riffle(letters) # => [1, 2, "a", "b", 3, 4, "c", 5, 6, "d", "e", "f"]

You may also pass an options Hash as the last argument to define the possible range of the randomly determined group size at each iteration:

numbers.riffle(letters, { min_group_size: 2, max_group_size: 8 })

Note on Random Subsequence Lengths

The resulting subsequence length from any given argument is random, so it is very likely that consecutive runs will produce different results.

numbers.riffle(letters) # => [1, "a", "b", 2, 3, "c", 4, 5, 6, "d", "e", "f"]
numbers.riffle(letters) # => [1, 2, 3, "a", "b", 4, 5, "c", "d", "e", 6, "f"]

Add this line to your application's Gemfile:

gem 'riffle'

And then execute:

$ bundle

Or install it yourself as:

$ gem install riffle

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

$ rspec spec