LeetCode--Permutation Sequence

class Solution {
public:
    string getPermutation(int n, int k) {
        int fac[10];
        bool vis[10];
        memset(vis, 0, sizeof(vis));
        fac[0] = 1;
        for(int i=1;i<10;i++)
            fac[i] = fac[i-1]*i;
        string res(n, '0');
        --k;
        for(int i=n-1;i>=0;i--){
            int temp = k/fac[i];
            int j=1;
            for(;j<10;j++){
                if(vis[j] == 0)
                    temp--;
                if(temp<0)
                    break;
            }
            res[n-i-1] = '0'+j;
            vis[j] = 1;
            k%=fac[i];
        }
        return res;
    }
};