<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 squares(vector<int> heights)
{
    int n=heights.size();
    int count=0;
    stack<int> st;
    for(int i=0;i<=n;i++)
    {
      while(!st.empty()&&(i==n || heights[st.top()]>=heights[i]))
      {
        int height=heights[st.top()];
        int width;
        st.pop();
        if(st.empty())width=i;
        else width=i-st.top()-1;
        int temp=min(height,width);
        temp=temp*temp;
        //cout<<height*width<<" ";
        count=max(count,temp);
      }
      st.push(i);
    }
   // cout<<endl;
    return count;
}
    int maximalSquare(vector<vector<char>>& matrix) {
                int ans=0;
        int m=matrix.size(),n=matrix[0].size();
                vector<int> height(n,0);
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                if(matrix[i][j]=='1')height[j]++;
                else height[j]=0;
               // cout<<height[j]<<" ";
            }
            //cout<<endl;
            ans=max(ans,squares(height));
        }
        return ans;
    }
};
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