<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>& heights) {
        stack<int>st;
        int n=heights.size();
        int maxArea=0;
        for(int i=0;i<=n;i++){
            while(!st.empty()&&(i==n||heights[st.top()]>heights[i])){
                int height=heights[st.top()];
                st.pop();
                int width=0;
                if(st.empty())width=i;
                else width=i-st.top()-1;
                int len=min(height,width);
                maxArea=max(maxArea,len*len);
            }
            st.push(i);
        }
        return maxArea;
    }
    int maximalSquare(vector<vector<char>>& matrix) {
        vector<int>temp;
        
        for(int i=0;i<matrix[0].size();i++)temp.push_back(matrix[0][i]=='1'?1:0);
        int mx=f(temp);
        for(int i=1;i<matrix.size();i++){
                 for(int j=0;j<matrix[i].size();j++){
                       if(matrix[i][j]=='1')temp[j]+=1;
                       else temp[j]=0;
                 }
                  mx=max(mx,f(temp));
        }
        return mx;
    }
};
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