Maximal Square

class Solution:
    def maximalSquare(self, matrix: List[List[str]]) -> int:

        res = 0
        for i in range(len(matrix)):
            for j in range(len(matrix[0])):
                matrix[i][j] = int(matrix[i][j])
                if i > 0 and j > 0 and matrix[i][j] == 1:
                    matrix[i][j] = min(matrix[i][j-1], matrix[i-1][j-1], matrix[i-1][j]) + 1
                res = max(res, matrix[i][j]**2)

        return res