Perfect Square

class Solution {
    public int numSquares(int n) {
        int[] dp = new int[n+1];
        if(n<=3){
            return n;
        }
        dp[0] = 0;
        dp[1] = 1;
        dp[2] = 2;
        dp[3] = 3;
        for(int i = 4; i<=n; i++){
            dp[i] = i;
            for(int j = 1; j <= Math.sqrt(i); j++){
                dp[i] = Math.min(dp[i], 1+dp[i-j*j]);
            }
        }
        return dp[n];
    }
}