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

if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {

return 0;

}

int rows = matrix.length;

int cols = matrix[0].length;

int[][] h = new int[rows][cols];

int max = 0;

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

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

h[i][j] = matrix[i][j] == '1' ? 1: 0;

if (i != 0 && h[i][j] != 0) {

h[i][j] = h[i - 1][j] + 1;

}

if (j == cols - 1) {

max = Math.max(max, maxArea(h[i]));

}

}

}

return max;

}

public int maxArea(int[] h) {

Stack<Integer> s = new Stack<Integer>();

int max = 0;

int i = 0;

// 注意，这里使用<= 因为当i到达最后，需要计算一次。

while (i <= h.length) {

//

if (s.isEmpty() || i < h.length && h[i] >= h[s.peek()]) {

s.push(i);

i++;

} else {

int height = h[s.pop()];

int width = s.isEmpty() ? i: i - s.peek() - 1;

max = Math.max(max, height * width);

}

}

return max;

}

}