<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 solve(int i, int j, int n, int m, vector<vector<char>>& mat,
              vector<vector<int>>& vis,vector<vector<int>>&dp) {
        if (i >= n || j >= m || mat[i][j] == '0')
            return 0;

       
        if(dp[i][j]!=-1)
          return dp[i][j];
        
        vis[i][j] = 1;
        int a = 1 + solve(i + 1, j, n, m, mat, vis,dp);
        int b = 1 + solve(i, j + 1, n, m, mat, vis,dp);
        int c = 1 + solve(i + 1, j + 1, n, m, mat, vis,dp);
        vis[i][j] = 0;
        return dp[i][j] = min(a, min(b, c));
    }
    int maximalSquare(vector<vector<char>>& matrix) {
        int n = matrix.size(), m = matrix[0].size();
        vector<vector<int>> vis(n, vector<int>(m, 0));
        vector<vector<int>>dp(n+1,vector<int>(m+1,-1));
        int ans = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (matrix[i][j] == '1' && vis[i][j] == 0) {
                    vis[i][j]=1;
                    int cnt = solve(i, j, n, m, matrix, vis,dp);
                    ans = max(ans, cnt);
                }
            }
        }
        return ans*ans;
    }
};
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