public int maximalSquare(char[][] matrix) {

int maxSquare = 0;

int m = matrix.length;

int n = matrix[0].length;

int minSide = Math.min(m, n);

for (int y = 0; y < m; y++) {

for (int x = 0; x < n; x++) {

char current = matrix[y][x];

if (x > 0 && y > 0) {

char left = matrix[y][x - 1];

char up = matrix[y - 1][x];

char diagonal = matrix[y - 1][x - 1];

int min = Math.min(Math.min(left, up), diagonal);

if (current == '1' && min > 0) {

current = (char) ++min;

} else {

current = (char) (current == '1' ? 1 : 0);

}

} else {

current = (char) (current == '1' ? 1 : 0);

}

if (current > maxSquare) maxSquare = current;

matrix[y][x] = current;

}

}

return maxSquare * maxSquare;

}

public static void main(String[] args) {

char[][] matrix = {{'1', '0', '1', '1', '1'}, {'1', '0', '1', '1', '1'}, {'1', '1', '1', '1', '1'}, {'1', '0', '0', '1', '0'}};

System.out.println(new Solution221().maximalSquare(matrix));

}