<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:
    def maximalSquare(self, matrix: List[List[str]]) -> int:
        memo={}
        def ms(matrix,n=0,m=0,m1=False):
            if m1==False:
                m1=True
                n=len(matrix)-1
                m=len(matrix[0])-1
            if (n,m) in memo : return memo[(n,m)]
            if n==0 and m==0:
                memo[(n,m)]=int(matrix[n][m])
                return memo[(n,m)]
            elif n==0:
                ms(matrix,n,m-1,m1)
                memo[(n,m)]=int(matrix[n][m])
                return memo[(n,m)]
            elif m==0:
                ms(matrix,n-1,m,m1)
                memo[(n,m)]=int(matrix[n][m])
                return memo[(n,m)]
            else: 
                value = int(matrix[n][m])
                match value:
                    case 0: 
                        ms(matrix,n,m-1,m1)
                        ms(matrix,n-1,m,m1)
                        ms(matrix,n-1,m-1,m1)
                        memo[(n,m)] = 0
                    case _:
                        memo[(n,m)]=min(ms(matrix,n,m-1,m1),ms(matrix,n-1,m,m1),ms(matrix,n-1,m-1,m1))+int(matrix[n][m])
                return memo[(n,m)]
        
        ms(matrix)
        max1=0
        for i in memo:
            if memo[i]>max1: max1=memo[i]
        return max1**2
        
54225