class Solution {
public:
    int numSquares(int n) {
        // dp[i] = least number of perfect square numbers
        vector<int> dp(n+1, 10001);
        dp[0] = 0;
        for(int i = 0; i <= n; i++) {
            for(int j = 1; j * j <= i; j++) {
                dp[i] = min(dp[i], dp[i - j*j] + 1);
            }
        }

        return dp[n] == 10001 ? 0 : dp[n];
    }
};