Perfect Squares

Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, …) which sum to n.

For example, given n = 12, return 3 because 12 = 4 + 4 + 4; given n = 13, return 2 because 13 = 4 + 9.

public class Solution {
    public int numSquares(int n) {
        int[] ans = new int[n+1];
        for(int i=1; i<=n; i++) ans[i] = Integer.MAX_VALUE;
        for(int i=1; i<=n; i++){
            for(int j=1; j*j<=i; j++){
                ans[i] = Math.min(ans[i], ans[i-j*j]+1);
            }
        }
        return ans[n];
    }
}