Leetcode:Maximal Rectangle 最大全1子矩阵

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

class Solution {
public:
    int maximalRectangle(vector<vector<char> > &matrix) {
        int nRow = matrix.size();
        if (nRow == 0) return 0;
        int nCol = matrix.at(0).size();
        std::vector<int> tmp(nCol, 0);
        int result = 0;
        for (int i = 0; i < nRow; ++i) {   // 计算每一行可以形成的最大矩形面积
            for (int j = 0; j < nCol; ++j) {
                if (matrix.at(i).at(j) == ‘0‘) {
                    tmp.at(j) = 0;
                } else {
                    tmp.at(j)++;         // 计算当前行的当前列的累积高度(1的个数)
                }
            }
            int area = largestRectangleArea(tmp);
            result = std::max(result, area);
        }
        return result;
    }
    
    // 最大矩形面积
    int largestRectangleArea(std::vector<int>& height) {
        if (height.size() == 0) return 0;
        height.push_back(-1);
        std::stack<int> stk;
        int result = 0;
        for (int i = 0; i < height.size(); ) {
            if (stk.empty() || height.at(i) > height.at(stk.top())) {
                stk.push(i);
                ++i;
            } else {
                int idx = stk.top();
                stk.pop();
                int area = height.at(idx) * (stk.empty() ? i : i - stk.top() - 1);
                result = std::max(result, area);
            }
        }
        return result;
    }
};