javascript - How to use programming algorithm to solve mathematical permutations and combinations?

Question

It seems that recursion is used, can you explain the idea?

Answer 1

var A = function(N,M,num){
    if( N < M || N <= 0) return 0;
    num = num || 1;
    if( M == 0 ) return num;
    return A(N-1,M-1,N * num);
};
//A排列

var C = function(N,M){
    return A(N,M) / A(M,M);
};
//C组合 ，应该就这样了

Answer 2

Refer to this article http://www.cnblogs.com/kaiye/...

Answer 3

github source code https://github.com/treeandgra...