您可以使用 Array.flatMap 在 Javascript 中返回 n 个选择 k 个组合吗？

Question

For instance, this is 5 choose 2:

 var array = [0,1,2,3,4]; var result = array.flatMap( (v, i) => array.slice(i+1).map(w => [v, w]) ); console.log(result);

How would I be able to do 5 choose 3 using this method?

Answer 1

Just add another level of nesting:

var array = [0,1,2,3,4];

var result = array.flatMap((v, i) =>
    array.slice(i+1).flatMap((w, j) =>
        array.slice(i+1+j+1).map(u =>
            [v, w, u]
        )
    )
);

console.log(result);

At this point, it might be easier to do with recursion though:

 function choose(arr, k, prefix=[]) { if (k == 0) return [prefix]; return arr.flatMap((v, i) => choose(arr.slice(i+1), k-1, [...prefix, v]) ); } console.log(choose([0,1,2,3,4], 3));