leetcode - Permutation Sequence

 

class Solution {
public:
    string getPermutation(int n, int k) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        string rlt="";
    unsigned *facts = new unsigned[n+1];
    unsigned * arr = new unsigned[n];
    facts[0] = 1;
    for (int i=1; i<=n; i++){
        facts[i] = facts[i-1] * i;
        arr[i-1] = i;
    }
    k = k-1;
    for (int i=1; i<n; i++){
        int offset  = k/facts[n-i];
        int  tmp = arr[i-1+offset];
        for (int j=i-1+offset; j>=i; j--){
        arr[j] = arr[j-1];
        }
        arr[i-1] = tmp;
        k = k % facts[n-i];
    }
           for (int i=0; i<n; i++)
        rlt = rlt + (char)('0'+arr[i]);
    delete []arr;
    delete []facts;
    return rlt;
    }
};