LeetCode OJ Maximal Rectangle

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

参考了求直方图的最大矩形，https://oj.leetcode.com/problems/largest-rectangle-in-histogram/，从上往下，将每一行及以上都看成直方图并求出最大矩形。

class Solution {
public:
    int maximalRectangle(vector<vector<char> > &matrix) {
        if (matrix.size() == 0) return 0;
        vector<int> height(matrix[0].size(), 0);  // record the height of every row's histogram
        int tempArea, maxArea = 0;
        for (int i = 0; i < matrix.size(); i++) {
            int j;
            for (j = 0; j < matrix[i].size(); j++) {  // calculate the height
                if (matrix[i][j] == '1') height[j]++;
                else height[j] = 0;
            }
            //calculate the max area of every histogram
            stack<int> s;
            for (j = 0; j < matrix[i].size();) {
                if (s.empty() || height[s.top()] <= height[j]) {
                    s.push(j++);
                } else {
                    int temp = s.top();
                    s.pop();
                    tempArea = height[temp] * (s.empty() ? j : j - s.top() - 1);
                    maxArea = tempArea > maxArea ? tempArea : maxArea;
                }
            }
            while (!s.empty()) {
                int temp = s.top();
                s.pop();
                tempArea = height[temp] * (s.empty() ? j : j - s.top() - 1);
                maxArea = tempArea > maxArea ? tempArea : maxArea;
            }
            //calculate the max area of every histogram
        }
        return maxArea;
    }
};