LeetCode-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.

应用直方图找矩形的函数 将每一行每一位上方的1的个数化为直方图，面积最大的矩形即都为1且面积最大的矩形

class Solution {
public:
     int largestRectangleArea(vector<int> &height) {
        if(height.size()==0)return 0;
        stack<pair<int,int> > sta;
        pair<int,int> p,q;
        int max=0;
        int start,end,area;
        for(int i=0;i<height.size();i++){
            p.first=height[i];
            p.second=i;
            if(sta.size()==0){
                sta.push(p);
            }
            else{
                while(sta.top().first>p.first){
                    q=sta.top();
                    sta.pop();
                    end=i-1;
                    if(sta.size()==0){
                        start=0;
                        area=q.first*(end-start+1);
                        if(area>max)max=area;
                        break;
                    }
                    else{
                        start=sta.top().second+1;
                        area=q.first*(end-start+1);
                        if(area>max)max=area;
                    }
                    
                }
                if(sta.size()!=0){
                    if(sta.top().first==p.first){
                        sta.top().second=i;
                    }
                    else{
                        sta.push(p);
                    }
                }
                else{
                    sta.push(p);
                }
            }
        }
        end=height.size()-1;
        while(sta.size()!=0){
            q=sta.top();
            sta.pop();
            if(sta.size()==0){
                start=0;
                area=q.first*(end-start+1);
                if(area>max)max=area;
            }
            else{
                start=sta.top().second+1;
                area=q.first*(end-start+1);
                if(area>max)max=area;
            }
        }
        return max;
    }
    int maximalRectangle(vector<vector<char> > &matrix) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(matrix.size()==0||matrix[0].size()==0){
            return 0;
        }
        vector<int> histogram;
        histogram.resize(matrix[0].size(),0);
        int max=0;
        for(int i=0;i<matrix.size();i++){
            for(int j=0;j<matrix[i].size();j++){
                if(matrix[i][j]=='1')histogram[j]++;
                else histogram[j]=0;
            }
            int v=largestRectangleArea(histogram); 
            if(v>max)max=v;
        }
        return max;
    }
};