LeetCode 85. 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(vector<vector<char>>& matrix) {
        int m = matrix.size();
        if (m == 0)
            return 0;
        int n = matrix[0].size();
        if (n == 0)
            return 0;
        
        vector<int> height(n, 0), left(n, 0), right(n, n - 1);
        int cur_left, cur_right, max_area = 0;
        for (int i = 0; i < m; ++i)
        {
            for (int j = 0; j < n; ++j)
                height[j] = (matrix[i][j] == '1') ? height[j] + 1 : 0;
            
            cur_left = 0;
            for (int j = 0; j < n; ++j)
            {
                if (matrix[i][j] == '1')
                    left[j] = max(left[j], cur_left);
                else
                {
                    left[j] = 0;
                    cur_left = j + 1;
                }
            }

            cur_right = n - 1;
            for (int j = n - 1; j >= 0; --j)
            {
                if (matrix[i][j] == '1')
                    right[j] = min(right[j], cur_right);
                else
                {
                    right[j] = n - 1;
                    cur_right = j - 1;
                }
            }

            for (int j = 0; j < n; ++j)
                max_area = max(max_area, height[j] * (right[j] - left[j] + 1));
        }
        return max_area;
    }
};