The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order, We get the following sequence (ie, for n = 3): "123" "132" "213" "231" "312" "321" Given n and k, return the kth permutation sequence. Note: Given n will be between 1 and 9 inclusive. http://leetcode.com/onlinejudge#question_60

leetcode_permutation_sequence.cpp

#define MAXN 10
int num[MAXN];

class Solution {
public:
    string getPermutation(int n, int k) {
        for (int i = 0; i < n; ++i)
            num[i] = i + 1;
        while (--k)
            next_permutation(num, num + n);
        stringstream is;
        for (int i = 0 ; i < n; ++i)
            is << num[i];
        string ans;
        is >> ans;
        return ans;
    }
};