<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:
vector<int> NSL(vector<int>&arr){
     int n= arr.size();
    vector<int>ans(n,-1);
    stack<int>st;
    for(int i=0;i<n;i++){
        while(!st.empty() && arr[st.top()]>=arr[i]){
            st.pop();
        }
        if(!st.empty()){
            ans[i]=st.top();
        }
        st.push(i);
    }
    return ans;
}
vector<int> NSR(vector<int>&arr){
     int n= arr.size();
    vector<int>ans(n,n);
    stack<int>st;
    for(int i=n-1;i>=0;i--){
        while(!st.empty() && arr[st.top()]>arr[i]){
            st.pop();
        }
        if(!st.empty()){
            ans[i]=st.top();
        }
        st.push(i);
    }
    return ans;
}
int findmaxarea(vector<int>&heights){
    vector<int>nsl=NSL(heights);
    vector<int>nsr=NSR(heights);
    int maxarea=INT_MIN;
    for(int i=0;i<heights.size();i++){
      int ans=nsr[i]-nsl[i]-1;
       ans=ans*heights[i];
       maxarea=max(maxarea,ans);
    }
    return maxarea;
}
    int maximalRectangle(vector<vector<char>>& matrix) {
        int n=matrix.size();
        int m= matrix[0].size();
        vector<int>height(m);
        for(int i=0;i<m;i++){
            height[i]=(matrix[0][i]=='1')? 1: 0;
        }
        int maxarea=findmaxarea(height);
        for(int row=1;row<n;row++){
            for(int col=0;col<m;col++){
                if(matrix[row][col]=='0'){
                    height[col]=0;
                }
                else{
                    height[col]+=1;
                }
            }
            maxarea=max(maxarea,findmaxarea(height));
        }
        return maxarea;
    }
};
21254