Leetcode 60. 第k个排列

用next_permutation函数

class Solution {
public:
    string getPermutation(int n, int k) {
        string s;
        for(int i=1;i<=n;++i) s+='0'+i;
        while(--k) next_permutation(s.begin(),s.end());
        return s;
    }
};