leetcode--Permutation Sequence

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):

1. "123"
2. "132"
3. "213"
4. "231"
5. "312"
6. "321"

Given n and k, return the k^th permutation sequence.

Note: Given n will be between 1 and 9 inclusive.

public class Solution {
    public String getPermutation(int n, int k) {
		ArrayList<Integer> data = new ArrayList<Integer>();
		int mod = 1;
		for(int i=1;i<=n;i++){
			data.add(i);
			mod *= i;
		}
		k--;
		String res = "";
		for(int i=0;i<n;i++){
			mod = mod/(n-i);
			int cur = k/mod;
			res += data.get(cur);
			data.remove(cur);
			k = k%mod;
		}
		return res;
    }
}