力扣 题目85- 最大矩形

题目

题解

一看这不是和力扣 题目84- 柱状图中最大的矩形差不多吗 那么我们以行 为一个柱状图 然后传入84题的过程不就可以了

例如第一行是 10100 而第二行是20211 即+1操作

特殊情况是0 如果有0的话那么当前柱子就会被截断

例如第四行 应该是4 0 0 3 0

                if (matrix[i][j] == '1') {
                    heights[j] += 1;
                }
                else {
                    heights[j] = 0;
                }

代码

#include<iostream>
#include<vector>
#include<stack>
using namespace std;
class Solution {
public:
    int maximalRectangle(vector<vector<char>>& matrix) {
        Solution sol;
        int area = 0;
        vector<int>heights(matrix[0].size(),0 );
        for (int i = 0; i < matrix.size(); i++) {
            for (int j = 0; j < matrix[i].size(); j++) {
                if (matrix[i][j] == '1') {
                    heights[j] += 1;
                }
                else {
                    heights[j] = 0;
                }
            }
            area = max(sol.largestRectangleArea(heights), area);
            //由于在84题 运算中加入了两个柱子帮助运算 所以这里要删除
            heights.pop_back();
            heights.erase(heights.begin());
        }
        return area;
    }

    int largestRectangleArea(vector<int>& heights) {
        heights.insert(heights.begin(), 0);
        heights.push_back(0);
        stack<int> stack;
        int area = 0;
        for (int i = 0; i < heights.size(); i++) {
            while (stack.size() != 0 && heights[i] < heights[stack.top()]) {
                int h = heights[stack.top()];
                stack.pop();
                area = max(area, (i - stack.top() - 1) * h);
            }
            stack.push(i);
        }
        return area;
    }
};

int main() {
    Solution sol;
    vector<vector<char>> matrix = { {'1','0','1','0','0'} ,{'1','0','1','1','1'},{'1','1','1','1','1'},{'1','0','0','1','0'} };
    int result = sol.maximalRectangle(matrix);
    cout << result << endl;
}