## Count number of squares in a rectangle

Given a m x n rectangle, how many squares are there in it?

class Solution {
public:
    int countSquares(int m, int n) {
        int count = 0;
        for (int i = 1; i <= min(m, n); ++i) {
            count += (m - i + 1) * (n - i + 1);
        }
        return count;    
    }
};

:::success
- 時間複雜度：$O(N)$
- 空間複雜度：$O(1)$
:::