279. 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 dp[] = new int[n+1];
        dp[0] = 0;
        for(int i = 1; i<=n; i++){
            dp[i] = Integer.MAX_VALUE;
            for(int j = 1; j*j<=i ;j++ ){
                if(dp[i] > dp[i - j*j] + 1){
                    dp[i] = dp[i-j*j] + 1;
                }
            }
        }
        return dp[n];
    }
}