Ruby 与数组元素的组合

Question

好的，我已经在互联网上搜索了答案，还在我的 ruby​​ 程序员中搜索了几个小时，但我无法解决这个问题。我正在编写一个脚本，用于根据数组中的元素进行各种组合。

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

此时我可以进行这些组合:

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

没关系，但我找不到搜索这些组合的方法，例如 ["a","c"] 或 ["a","c","d"] 或 [ "a","d"] 等...

现在我的代码是这样的:

def combinaties(array)
  combinaties = []
  i=0
  while i <= array.length-1
    combinaties << array[i]
    unless i == array.length-1
      array[(i+1)..(array.length-1)].each{|volgend_element|
        combinaties<<(combinaties.last.dup<<volgend_element)
      }
    end
    i+=1
  end
end

Answer 1

Functional方法(需要 Ruby >= 1.9)来创建 powerset数组的(除了你似乎不需要的空元素):

xs = ["a", "b", "c", "d"]
yss = 1.upto(xs.size).flat_map do |n|
  xs.combination(n).to_a
end

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