int maximalSquare(vector<vector<char>>& matrix) {

if (matrix.size() == 0 || matrix[0].size() == 0) {

return 0;

}

int maxSide = 0;

int rows = matrix.size(), columns = matrix[0].size();

vector<vector<int>> dp(rows, vector<int>(columns));

for (int i = 0; i < rows; i++) {

for (int j = 0; j < columns; j++) {

if (matrix[i][j] == '1') {

if (i == 0 || j == 0) {

dp[i][j] = 1;

} else {

dp[i][j] = min(min(dp[i - 1][j], dp[i][j - 1]), dp[i - 1][j - 1]) + 1;

}

maxSide = max(maxSide, dp[i][j]);

}

}

}

int maxSquare = maxSide * maxSide;

return maxSquare;

}