
java
class Solution {
public int maximalSquare(char[][] matrix) {
int result = 0; // 记录正方形边长
int m = matrix.length, n = matrix[0].length;
int[][] dp = new int[m + 1][n + 1];
// 动态规划
for (int i = 1; i <= m; i++) {
for (int j = 1; j <= n; j++) {
if (matrix[i - 1][j - 1] == '0') {
dp[i][j] = 0;
} else {
dp[i][j] = 1 + Math.min(Math.min(dp[i - 1][j], dp[i][j - 1]), dp[i - 1][j - 1]);
result = Math.max(result, dp[i][j]);
}
}
}
return result * result;
}
}