ruby-on-rails - 数组的所有变体

Question

我有一个结构如下的数组:

  array = ["one","two","three","four"];

我怎样才能得到这个数组所有可能的变体，所有可能的长度 1-4:

  ar = [["one"]["two"]["three"]["four"]["one","two"]
       ["one","three"] ["one","three","four"]]

我觉得最后数组应该有4*4*4*4个元素

Answer 1

How can i get all possible variants of this array[...]

使用Array#combination :

array.combination(3).to_a

结果:

[["one", "two", "three"],
 ["one", "two", "four"],
 ["one", "three", "four"],
 ["two", "three", "four"]]

[...]in all possible lengths 1-4

使用一个范围，用 Enumerable#flat_map 遍历它:

(1..array.length).flat_map {|len| array.combination(len).to_a }

结果:

[["one"],
 ["two"],
 ["three"],
 ["four"],
 ["one", "two"],
 ["one", "three"],
 ["one", "four"],
 ["two", "three"],
 ["two", "four"],
 ["three", "four"],
 ["one", "two", "three"],
 ["one", "two", "four"],
 ["one", "three", "four"],
 ["two", "three", "four"],
 ["one", "two", "three", "four"]]