Q85 最大矩形

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<Integer> 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;
    }
}