<p>Given a <code>rows x cols</code>&nbsp;binary <code>matrix</code> filled with <code>0</code>&#39;s and <code>1</code>&#39;s, find the largest rectangle containing only <code>1</code>&#39;s and return <em>its area</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/09/14/maximal.jpg" style="width: 402px; height: 322px;" />
<pre>
<strong>Input:</strong> matrix = [[&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;],[&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;],[&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;],[&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;]]
<strong>Output:</strong> 6
<strong>Explanation:</strong> The maximal rectangle is shown in the above picture.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> matrix = [[&quot;0&quot;]]
<strong>Output:</strong> 0
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> matrix = [[&quot;1&quot;]]
<strong>Output:</strong> 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>rows == matrix.length</code></li>
	<li><code>cols == matrix[i].length</code></li>
	<li><code>1 &lt;= row, cols &lt;= 200</code></li>
	<li><code>matrix[i][j]</code> is <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
</ul>

class Solution {
public:
    int maximalRectangle(vector<vector<char>>& matrix) {
        int n = matrix.size();
        int m = matrix[0].size();
        // for(auto u : matrix){
        //     for(auto c : u ){
        //         cout<<c<<" ";
        //     }
        //     cout<<endl;
        // }
        vector<vector<pair<int,int>>> v(n,vector<pair<int,int>>(m));
        for(int i =n-1 ;i>=0 ;i--){
            for(int j =m-1 ;j>=0 ;j--){
                int r =0 ;
                int c =0 ;
                int check=1;
                for(int k=j ; k<m; k++){
                    if(check==0)break;
                    if(matrix[i][k]=='1'){
                        r++;
                    }else{
                        check=0;
                    }
                }
                check=1;
                for(int k=i ;k<n;k++){
                    if(check==0)break;
                    if(matrix[k][j]=='1'){
                        c++;
                    }
                    else{
                        check=0;
                    }
                }
                v[i][j].first=r;
                v[i][j].second=c;
            }
        }
        int ans=0;
        // for(auto u : v){
        //     for(auto c : u ){
        //         cout<<c.first<<" ";
        //     }
        //     cout<<endl;
        // }
        for(int i =0 ;i<n;i++){
            for(int j=0 ;j<m ;j++){
                int rec =0 ;
                int mx =m;
                for(int k=i ;k<n;k++){
                    mx=min(mx,v[k][j].first);
                    rec= max(rec,mx*(k-(i-1)));
                }
                // cout<<rec<<" ";
                ans=max(ans,rec);
            }
            // cout<<endl;
        }
        return ans;
    }
};
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