javascript - 获取所有可能的元素组合

Question

如何获得数组中 2 个元素的所有可能组合？

例如:

[
    1, 
    2, 
    3, 
    4 
]

becomes

[
    [1, 2], 
    [1, 3], 
    [1, 4], 
    [2, 1], 
    [2, 3], 
    [2, 4],
    [3, 1],
    [3, 2],
    [3, 4],
    [4, 1],
    [4, 2],
    [4, 3] 
]

此答案使用蛮力，但是否有 Ramda 和/或柯里化(Currying)的实用方法？ Derive every possible combination of elements in array

Answer 1

这是一个优雅的解决方案:

//    permutations :: Number -> [a] -> [[a]]
const permutations = R.compose(R.sequence(R.of), R.flip(R.repeat));

使用示例:

permutations(2, [1, 2, 3, 4]);
// => [[1, 1], [1, 2], ..., [4, 3], [4, 4]]

permutations(3, [1, 2, 3, 4]);
// => [[1, 1, 1], [1, 1, 2], ..., [4, 4, 3], [4, 4, 4]]