leetcode-problemset/leetcode-cn/problem (English)/最大的以 1 为边界的正方形(English) [largest-1-bordered-square].html

<p>Given a 2D <code>grid</code> of <code>0</code>s and <code>1</code>s, return the number of elements in&nbsp;the largest <strong>square</strong>&nbsp;subgrid that has all <code>1</code>s on its <strong>border</strong>, or <code>0</code> if such a subgrid&nbsp;doesn&#39;t exist in the <code>grid</code>.</p>



<p>&nbsp;</p>

<p><strong>Example 1:</strong></p>



<pre>

<strong>Input:</strong> grid = [[1,1,1],[1,0,1],[1,1,1]]

<strong>Output:</strong> 9

</pre>



<p><strong>Example 2:</strong></p>



<pre>

<strong>Input:</strong> grid = [[1,1,0,0]]

<strong>Output:</strong> 1

</pre>



<p>&nbsp;</p>

<p><strong>Constraints:</strong></p>



<ul>

	<li><code>1 &lt;= grid.length &lt;= 100</code></li>

	<li><code>1 &lt;= grid[0].length &lt;= 100</code></li>

	<li><code>grid[i][j]</code> is <code>0</code> or <code>1</code></li>

</ul>