<p>Given an <code>m x n</code> binary <code>matrix</code> filled with <code>0</code>&#39;s and <code>1</code>&#39;s, <em>find the largest square containing only</em> <code>1</code>&#39;s <em>and return its area</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/26/max1grid.jpg" style="width: 400px; height: 319px;" />
<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> 4
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/26/max2grid.jpg" style="width: 165px; height: 165px;" />
<pre>
<strong>Input:</strong> matrix = [[&quot;0&quot;,&quot;1&quot;],[&quot;1&quot;,&quot;0&quot;]]
<strong>Output:</strong> 1
</pre>

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

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

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

<ul>
	<li><code>m == matrix.length</code></li>
	<li><code>n == matrix[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 300</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 f(vector<int>&height)
    {
        stack<int>st;
        int maxi=0;
        int n=height.size();
        for(int i=0;i<=n;i++)
        {
            while(!st.empty() && (i==n || height[st.top()]>=height[i]))
            {
                int ht=height[st.top()];
                st.pop();
                int width=1;
                if(st.empty())
                {
                    width=i;
                }
                else
                {
                    width=i-st.top()-1;
                }
                 int side = min(width, ht);
                maxi=max(maxi,side*side);
            }
            st.push(i);
            
        }      
        return maxi;

    }
    int maximalSquare(vector<vector<char>>& matrix) 
    {
        int m=matrix.size();
        int n=matrix[0].size();
        vector<int>arr(n,0);
        int maxi=INT_MIN;
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                // cout<<i<<" "<<j<<endl;
                if(matrix[i][j]=='1')
                {
                    // cout<<i<<" "<<j<<endl;
                    arr[j]++;
                }
                else if(matrix[i][j]=='0')
                {
                    if(arr[j]!=0)
                    {
                        arr[j]=0;

                    }
                }
            }
       
            int p=f(arr);
            maxi=max(maxi,p);

        }
        return maxi;


        
    }
};
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