leetcode-problemset/leetcode-cn/problem (English)/旋转盒子(English) [rotating-the-box].html

<p>You are given an <code>m x n</code> matrix of characters <code>boxGrid</code> representing a side-view of a box. Each cell of the box is one of the following:</p>

<ul>
	<li>A stone <code>&#39;#&#39;</code></li>
	<li>A stationary obstacle <code>&#39;*&#39;</code></li>
	<li>Empty <code>&#39;.&#39;</code></li>
</ul>

<p>The box is rotated <strong>90 degrees clockwise</strong>, causing some of the stones to fall due to gravity. Each stone falls down until it lands on an obstacle, another stone, or the bottom of the box. Gravity <strong>does not</strong> affect the obstacles&#39; positions, and the inertia from the box&#39;s rotation <strong>does not </strong>affect the stones&#39; horizontal positions.</p>

<p>It is <strong>guaranteed</strong> that each stone in <code>boxGrid</code> rests on an obstacle, another stone, or the bottom of the box.</p>

<p>Return <em>an </em><code>n x m</code><em> matrix representing the box after the rotation described above</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2021/04/08/rotatingtheboxleetcodewithstones.png" style="width: 300px; height: 150px;" /></p>

<pre>
<strong>Input:</strong> boxGrid = [[&quot;#&quot;,&quot;.&quot;,&quot;#&quot;]]
<strong>Output:</strong> [[&quot;.&quot;],
&nbsp;        [&quot;#&quot;],
&nbsp;        [&quot;#&quot;]]
</pre>

<p><strong class="example">Example 2:</strong></p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2021/04/08/rotatingtheboxleetcode2withstones.png" style="width: 375px; height: 195px;" /></p>

<pre>
<strong>Input:</strong> boxGrid = [[&quot;#&quot;,&quot;.&quot;,&quot;*&quot;,&quot;.&quot;],
&nbsp;             [&quot;#&quot;,&quot;#&quot;,&quot;*&quot;,&quot;.&quot;]]
<strong>Output:</strong> [[&quot;#&quot;,&quot;.&quot;],
&nbsp;        [&quot;#&quot;,&quot;#&quot;],
&nbsp;        [&quot;*&quot;,&quot;*&quot;],
&nbsp;        [&quot;.&quot;,&quot;.&quot;]]
</pre>

<p><strong class="example">Example 3:</strong></p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2021/04/08/rotatingtheboxleetcode3withstone.png" style="width: 400px; height: 218px;" /></p>

<pre>
<strong>Input:</strong> boxGrid = [[&quot;#&quot;,&quot;#&quot;,&quot;*&quot;,&quot;.&quot;,&quot;*&quot;,&quot;.&quot;],
&nbsp;             [&quot;#&quot;,&quot;#&quot;,&quot;#&quot;,&quot;*&quot;,&quot;.&quot;,&quot;.&quot;],
&nbsp;             [&quot;#&quot;,&quot;#&quot;,&quot;#&quot;,&quot;.&quot;,&quot;#&quot;,&quot;.&quot;]]
<strong>Output:</strong> [[&quot;.&quot;,&quot;#&quot;,&quot;#&quot;],
&nbsp;        [&quot;.&quot;,&quot;#&quot;,&quot;#&quot;],
&nbsp;        [&quot;#&quot;,&quot;#&quot;,&quot;*&quot;],
&nbsp;        [&quot;#&quot;,&quot;*&quot;,&quot;.&quot;],
&nbsp;        [&quot;#&quot;,&quot;.&quot;,&quot;*&quot;],
&nbsp;        [&quot;#&quot;,&quot;.&quot;,&quot;.&quot;]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == boxGrid.length</code></li>
	<li><code>n == boxGrid[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 500</code></li>
	<li><code>boxGrid[i][j]</code> is either <code>&#39;#&#39;</code>, <code>&#39;*&#39;</code>, or <code>&#39;.&#39;</code>.</li>
</ul>