LeetCode开心刷题三十二天——85. Maximal Rectangle

#include<stdio.h>
#include<iostream>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<algorithm>
#include<climits>
using namespace std;
class Solution {
public:
    int maximalRectangle(vector<vector<char>>& matrix) {
        //NULL judge very important
        int n1=matrix.size();
        if(n1==0) return 0;
        int n2=matrix[0].size();
        //dp[i][j] is the max number of 1 in columns j rows i
        //vector initializer special no need ==
        vector<vector<int>> dp(n1,vector<int>(n2));
        //initialization
        for(int i=0;i<n1;i++)
        {
            for(int j=0;j<n2;j++)
            {
                //nested function need to pay attention whether finish all procedure such as this finish one easy to forget the latter ?:
                dp[i][j]=(matrix[i][j]==‘1‘)?(j==0?1:dp[i][j-1]+1):0;
            }
        }

        int ans=0;

        for(int i=0;i<n1;i++)
        {
            for(int j=0;j<n2;j++)
            {
                int len = INT_MAX;
                for(int k=i;k<n1;k++)
                {
                    len=min(len,dp[k][j]);
                    if(len==0) break;
                    ans=max((k-i+1)*len,ans);
                }
            }
        }

        return ans;
    }
};

int main()
{
    vector<vector<char>> matrix=
    {
        {‘1‘,‘0‘,‘1‘,‘0‘},{‘1‘,‘1‘},‘0‘}
    };
    Solution s;
    int res=s.maximalRectangle(matrix);
    cout<<res<<endl;
    return 0;
}