Leetcode#60||Permutation Sequence

public class Solution {
    public String getPermutation(int n, int k) {
        StringBuilder result = new StringBuilder();
        List<Integer> list = new ArrayList<Integer>();
        
        int factorial = 1;
        for (int i = 1; i <= n; i++) {
            list.add(i);
            factorial *= i;
        }
        
        k--;
        
        for (int i = n; i > 0; i--) {
            factorial /= i;
            
            int index = k / factorial;
            k = k % factorial;
            
            result.append(list.get(index));
            list.remove(index);
        }
        
        return result.toString();
    }
}