Method: Array#combination

Defined in:
lib/core/facets/array/combination.rb

#combination(k = 2) ⇒ Object

Yields the block to each unique combination of n elements.

a = %w|a b c d|
a.combination(3)

produces

[["a", "b", "c"],
 ["a", "b", "d"],
 ["a", "c", "d"],
 ["b", "c", "d"]]

CREDIT: Florian Gross



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# File 'lib/core/facets/array/combination.rb', line 21

def combination(k=2)
  if block_given?
    s = to_a
    n = s.size
    return unless (1..n) === k
    idx = (0...k).to_a
    loop do
      yield s.values_at(*idx)
      i = k - 1
      i -= 1 while idx[i] == n - k + i
      break if i < 0
      idx[i] += 1
      (i + 1 ... k).each {|j| idx[j] = idx[i] + j - i}
    end
  else
    to_enum(:combination, k)
  end
end