leetcode-problemset/leetcode-cn/problem (English)/矩阵中的蛇(English) [snake-in-matrix].html

<p>There is a snake in an <code>n x n</code> matrix <code>grid</code> and can move in <strong>four possible directions</strong>. Each cell in the <code>grid</code> is identified by the position: <code>grid[i][j] = (i * n) + j</code>.</p>

<p>The snake starts at cell 0 and follows a sequence of commands.</p>

<p>You are given an integer <code>n</code> representing the size of the <code>grid</code> and an array of strings <code>commands</code> where each <code>command[i]</code> is either <code>&quot;UP&quot;</code>, <code>&quot;RIGHT&quot;</code>, <code>&quot;DOWN&quot;</code>, and <code>&quot;LEFT&quot;</code>. It&#39;s guaranteed that the snake will remain within the <code>grid</code> boundaries throughout its movement.</p>

<p>Return the position of the final cell where the snake ends up after executing <code>commands</code>.</p>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">n = 2, commands = [&quot;RIGHT&quot;,&quot;DOWN&quot;]</span></p>

<p><strong>Output:</strong> <span class="example-io">3</span></p>

<p><strong>Explanation:</strong></p>

<div style="display:flex; gap: 12px;">
<table border="1" cellspacing="3" style="border-collapse: separate; text-align: center;">
	<tbody>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid red; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">0</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">1</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">2</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">3</td>
		</tr>
	</tbody>
</table>

<table border="1" cellspacing="3" style="border-collapse: separate; text-align: center;">
	<tbody>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">0</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid red; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">1</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">2</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">3</td>
		</tr>
	</tbody>
</table>

<table border="1" cellspacing="3" style="border-collapse: separate; text-align: center;">
	<tbody>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">0</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">1</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">2</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid red; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">3</td>
		</tr>
	</tbody>
</table>
</div>
</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">n = 3, commands = [&quot;DOWN&quot;,&quot;RIGHT&quot;,&quot;UP&quot;]</span></p>

<p><strong>Output:</strong> <span class="example-io">1</span></p>

<p><strong>Explanation:</strong></p>

<div style="display:flex; gap: 12px;">
<table border="1" cellspacing="3" style="border-collapse: separate; text-align: center;">
	<tbody>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid red; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">0</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">1</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">2</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">3</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">4</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">5</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">6</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">7</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">8</td>
		</tr>
	</tbody>
</table>

<table border="1" cellspacing="3" style="border-collapse: separate; text-align: center;">
	<tbody>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">0</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">1</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">2</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid red; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">3</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">4</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">5</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">6</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">7</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">8</td>
		</tr>
	</tbody>
</table>

<table border="1" cellspacing="3" style="border-collapse: separate; text-align: center;">
	<tbody>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">0</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">1</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">2</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">3</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid red; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">4</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">5</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">6</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">7</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">8</td>
		</tr>
	</tbody>
</table>

<table border="1" cellspacing="3" style="border-collapse: separate; text-align: center;">
	<tbody>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">0</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid red; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">1</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">2</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">3</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">4</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #b30000; --darkreader-inline-border-right: #b30000; --darkreader-inline-border-bottom: #b30000; --darkreader-inline-border-left: #b30000;">5</td>
		</tr>
		<tr>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">6</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">7</td>
			<td data-darkreader-inline-border-bottom="" data-darkreader-inline-border-left="" data-darkreader-inline-border-right="" data-darkreader-inline-border-top="" style="padding: 5px 10px; border: 1px solid black; --darkreader-inline-border-top: #8c8273; --darkreader-inline-border-right: #8c8273; --darkreader-inline-border-bottom: #8c8273; --darkreader-inline-border-left: #8c8273;">8</td>
		</tr>
	</tbody>
</table>
</div>
</div>

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

<ul>
	<li><code>2 &lt;= n &lt;= 10</code></li>
	<li><code>1 &lt;= commands.length &lt;= 100</code></li>
	<li><code>commands</code> consists only of <code>&quot;UP&quot;</code>, <code>&quot;RIGHT&quot;</code>, <code>&quot;DOWN&quot;</code>, and <code>&quot;LEFT&quot;</code>.</li>
	<li>The input is generated such the snake will not move outside of the boundaries.</li>
</ul>