221. Maximal Square

class Solution {
public:
    int maximalSquare(vector<vector<char>>& matrix)
    {
        int m = matrix.size(), n = matrix[0].size();
        vector<vector<int>> dp(m, vector<int>(n));
        int d = 0;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (i == 0 || j == 0) {
                    dp[i][j] = matrix[i][j] - '0';
                } else if (matrix[i][j] == '1') {
                    dp[i][j] = min({dp[i - 1][j - 1], dp[i - 1][j], dp[i][j - 1]}) + 1;
                }
                d = max(d, dp[i][j]);
            }
        }
        return d * d;
    }
};

• T: $O(M \cdot N)$
• S: $O(M \cdot N)$

2 - Space Improved