LeetCode 60. Permutation Sequence

class Solution {
public:
    int fact[15];
    string getPermutation(int n, int k) {
        
        fact[0]=1;
        
        for(int i=1;i<=n;i++)
        {
            fact[i]=fact[i-1]*i;
        }
        
        string s="";
        int vis[15];
        k--;
        memset(vis,0,sizeof(vis));
        for(int i=0;i<n;i++)
        {
            int x = k / fact[n-i-1];
            int j;
            for( j=1;j<=n;j++)
            {
                if(vis[j]==0)
                {
                    if(x==0) break;
                    x--;    
                }
            }
            
            s+=(j+'0');
            vis[j]=1;
            
            k%=fact[n-i-1];
        }
        
        return s;
    }
};