clojure：子集的排列？(clojure: permutations of subsets?)

clojure：子集的排列？(clojure: permutations of subsets?)

我是clojure的新手，正在寻找一个函数来生成子集的排列：

=> (find-subsets 1 #{1 2 3 4}) (#{1} #{2} #{3} #{4}) => (find-subsets 2 #{1 2 3 4}) (#{1 2} #{1 3} #{1 4} #{2 3} #{2 4} #{3 4}) => (find-subsets 3 #{1 2 3 4}) (#{1 2 3} #{1 3 4} #{2 3 4})

这样的事情存在吗？ 如果没有，是否有一个很好的，干净的，惯用的方式来编写功能？

I'm new to clojure, looking for a function to generate permutations of subsets:

=> (find-subsets 1 #{1 2 3 4}) (#{1} #{2} #{3} #{4}) => (find-subsets 2 #{1 2 3 4}) (#{1 2} #{1 3} #{1 4} #{2 3} #{2 4} #{3 4}) => (find-subsets 3 #{1 2 3 4}) (#{1 2 3} #{1 3 4} #{2 3 4})

Does such a thing exist? If not, is there a nice, clean, idiomatic way to code the function?

最满意答案

看一下组合学 。 它满足你的需求：

; all the unique ways of taking n different elements from items (clojure.math.combinatorics/combinations [1 2 3] 2) ;;=> ((1 2) (1 3) (2 3))

如果因为使用集合而不是矢量而抱怨，只需在调用combinations之前将其转换为带矢量的矢量。

Take a look at combinatorics. It does what you need:

; all the unique ways of taking n different elements from items (clojure.math.combinatorics/combinations [1 2 3] 2) ;;=> ((1 2) (1 3) (2 3))

If it complains because you use a set instead of a vector, just convert to vector with vec before calling combinations.