leetcode 221. Maximal Square

class Solution(object):
def maximalSquare(self, matrix):
"""
:type matrix: List[List[str]]
:rtype: int
"""
if not matrix:
return 0
res = 0
m,n = len(matrix),len(matrix[0])
dp = [[ 0 for i in range(n)] for j in range(m)]
for i in range(m):
for j in range(n):
if i == 0 or j == 0:
dp[i][j] = int(matrix[i][j])
else:
if matrix[i][j] == '1':
dp[i][j] = min(dp[i-1][j],dp[i][j-1],dp[i-1][j-1]) + 1
else:
dp[i][j] = 0
res = max(res,dp[i][j])
return res ** 2