给定一个仅包含 0 和 1 的二维二进制矩阵，找出只包含 1 的最大矩形，并返回其面积。

示例:

输入:[  ["1","0","1","0","0"],  ["1","0","1","1","1"],  ["1","1","1","1","1"],  ["1","0","0","1","0"]]输出: 6

class Solution {    public int maximalRectangle(char[][] matrix) {        if (matrix == null || matrix.length == 0 || matrix[0].length == 0)            return 0;        int[] sum = new int[matrix[0].length];        int max = 0;        for (int i = 0; i < matrix.length; i++) {            for (int j = 0; j < matrix[0].length; j++) {                sum[j] = matrix[i][j] == '0' ? 0 : sum[j] + 1;            }            int t = findMax(sum);            max = max > t ? max : t;        }        return max;    }    private int findMax(int[] nums) {        int max = 0;        Deque
     
       stack = new LinkedList<>();        for (int i = 0; i < nums.length; i++) {            while (!stack.isEmpty() && nums[stack.peek()] >= nums[i]) {                int j = stack.pop();                int left = stack.isEmpty() ? -1 : stack.peek();                int size = (i - left - 1) * nums[j];                max = max > size ? max : size;            }            stack.push(i);        }        while (!stack.isEmpty()) {            int j = stack.pop();            int left = stack.isEmpty() ? -1 : stack.peek();            int size = (nums.length - left - 1) * nums[j];            max = max > size ? max : size;        }        return max;    }}