Ruby 1.9.2 リファレンスマニュアル > ライブラリ一覧 > 組み込みライブラリ > Arrayクラス > repeated_combination

instance method Array#repeated_combination

repeated_combination(n) { |c| block } -> Array

repeated_combination(n) -> Enumerator

When invoked with a block, yields all repeated combinations of length <i>n</i> of elements from <i>ary</i> and then returns <i>ary</i> itself. The implementation makes no guarantees about the order in which the repeated combinations are yielded.

When invoked without a block, returns an enumerator object instead.

Examples:

a = [1, 2, 3]
a.repeated_combination(1).to_a  #=> [[1], [2], [3]]
a.repeated_combination(2).to_a  #=> [[1,1],[1,2],[1,3],[2,2],[2,3],[3,3]]
a.repeated_combination(3).to_a  #=> [[1,1,1],[1,1,2],[1,1,3],[1,2,2],[1,2,3],
                                #    [1,3,3],[2,2,2],[2,2,3],[2,3,3],[3,3,3]]
a.repeated_combination(4).to_a  #=> [[1,1,1,1],[1,1,1,2],[1,1,1,3],[1,1,2,2],[1,1,2,3],
                                #    [1,1,3,3],[1,2,2,2],[1,2,2,3],[1,2,3,3],[1,3,3,3],
                                #    [2,2,2,2],[2,2,2,3],[2,2,3,3],[2,3,3,3],[3,3,3,3]]
a.repeated_combination(0).to_a  #=> [[]] # one combination of length 0

[SEE_ALSO] Array#repeated_permutation, Array#combination