生成所有候选条件的给定范围内的一个长度的阵列的组合

问题描述

如何可以生成一个给定的范围内，长度的数组元素的所有可能的组合？例如：

How can I generate all possible combinations of elements of an array with a length within a given range? E.g.:

('a'..'f').to_a.all_possibilities(3, 5)

应该产生一个数组，如：

should produce an array like:

['abc', 'abd', 'abe', 'abf', ..., 'abcde', 'abcdf', 'abcda', ...]

包括ABC（三个字符）到（'A'..'F'）。to_a的最后一个可能的组合与五个字符长度。我不知道如何做到这一点。任何帮助吗？

including from "abc" (three characters) up to the last possible combination of ('a'..'f').to_a with five characters length. I have no idea how to do this. Any help?

推荐答案

<$c$c>Array#combination是STDLIB：

Array#combination is stdlib:

[1] pry(main)> a = ('a'..'f').to_a
=> ["a", "b", "c", "d", "e", "f"]
[2] pry(main)> a.combination(3).to_a
=> [["a", "b", "c"],
 ["a", "b", "d"],
 ["a", "b", "e"],
 ["a", "b", "f"],
 ["a", "c", "d"],
 ["a", "c", "e"],
 ["a", "c", "f"],
 ["a", "d", "e"],
 ["a", "d", "f"],
 ["a", "e", "f"],
 ["b", "c", "d"],
 ["b", "c", "e"],
 ["b", "c", "f"],
 ["b", "d", "e"],
 ["b", "d", "f"],
 ["b", "e", "f"],
 ["c", "d", "e"],
 ["c", "d", "f"],
 ["c", "e", "f"],
 ["d", "e", "f"]]

如果你想要的大小分所有组合到最大：

if you want all combinations of size min to max:

(min..max).flat_map{|size| a.combination(size).to_a }

如果您希望它们转换为字符串，只需更换 .to_a 与 .MAP（安培;：加入）

If you want them converted to strings, just replace .to_a with .map(&:join).

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