Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.

 1 public class Solution {
 2     public int maximalRectangle(char[][] matrix) {
 3         if (matrix==null || matrix.length==0 || matrix[0].length==0) return 0;
 4         int[] height = new int[matrix[0].length];
 5         int maxArea = 0;
 6
 7         for (int row=0; row<matrix.length; row++) {
 8             LinkedList<Integer> stack = new LinkedList<Integer>();
 9             for (int i=0; i<matrix[0].length; i++) {
10                 if (matrix[row][i] != '0') height[i] = height[i] + 1;
11                 else height[i] = 0;
12             }
13             for (int col=0; col<matrix[0].length; col++) {
14                 if (stack.size()==0 || height[col]>height[stack.peek()]) {
15                     stack.push(col);
16                 }
17                 else {
18                     int temp = stack.pop();
19                     int width = (stack.size()==0)? col : col-stack.peek()-1;
20                     maxArea = Math.max(maxArea, width*height[temp]);
21                     col--;
22                 }
23             }
24             while (stack.size() != 0) {
25                 int temp = stack.pop();
26                 int width = (stack.size()==0)? height.length : height.length-stack.peek()-1;
27                 maxArea = Math.max(maxArea, width*height[temp]);
28             }
29         }
30
31         return maxArea;
32     }
33 }