<p>Given a 2D integer array <code>matrix</code>, return <em>the <strong>transpose</strong> of</em> <code>matrix</code>.</p>

<p>The <strong>transpose</strong> of a matrix is the matrix flipped over its main diagonal, switching the matrix&#39;s row and column indices.</p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2021/02/10/hint_transpose.png" style="width: 600px; height: 197px;" /></p>

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

<pre>
<strong>Input:</strong> matrix = [[1,2,3],[4,5,6],[7,8,9]]
<strong>Output:</strong> [[1,4,7],[2,5,8],[3,6,9]]
</pre>

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

<pre>
<strong>Input:</strong> matrix = [[1,2,3],[4,5,6]]
<strong>Output:</strong> [[1,4],[2,5],[3,6]]
</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;= 1000</code></li>
	<li><code>1 &lt;= m * n &lt;= 10<sup>5</sup></code></li>
	<li><code>-10<sup>9</sup> &lt;= matrix[i][j] &lt;= 10<sup>9</sup></code></li>
</ul>