<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 largestRectangleArea(vector<int>& heights) {
        int n = heights.size();
        if(n==1) return heights[0];
        stack<int> st;
        st.push(-1);
        int ans=0;
        int height =0;
        int width = 0;
        for(int i=0;i<n;i++){
            while(st.top()!=-1 && heights[st.top()]>=heights[i]){
                height = heights[st.top()];
                st.pop();
                width = i-st.top()-1;
                int m = min(height,width);
                ans = max(ans,m*m); 
            }
            st.push(i);
        }
        while(st.top()!=-1){
            height = heights[st.top()];
            st.pop();
            width = heights.size()-st.top()-1;
            int m = min(height,width);
            ans = max(ans,m*m); 
        }
       // cout<<ans<<" "<<heights[0]<<"\n";
        return ans;
    }

    int maximalSquare(vector<vector<char>>& matrix) {
        int n = matrix.size();
        int m = matrix[0].size();
        vector<vector<int>> dp(n+1,vector<int>(m+1,0));

        for(int i=1;i<=n;i++){
            for(int j=1;j<=m;j++){
                dp[i][j] = (matrix[i-1][j-1]=='1')? dp[i-1][j]+matrix[i-1][j-1]-'0':matrix[i-1][j-1]-'0';
               // cout<<dp[i][j]<<" ";
            }
            //cout<<"\n";
        }

        int ans=0;
        for(int i=1;i<=n;i++){
            ans = max(ans,largestRectangleArea(dp[i]));
        }
        return ans;


    }
};
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