leetcode-problemset/leetcode/problem/concatenation-of-array.html

<p>Given an integer array <code>nums</code> of length <code>n</code>, you want to create an array <code>ans</code> of length <code>2n</code> where <code>ans[i] == nums[i]</code> and <code>ans[i + n] == nums[i]</code> for <code>0 &lt;= i &lt; n</code> (<strong>0-indexed</strong>).</p>

<p>Specifically, <code>ans</code> is the <strong>concatenation</strong> of two <code>nums</code> arrays.</p>

<p>Return <em>the array </em><code>ans</code>.</p>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,1]
<strong>Output:</strong> [1,2,1,1,2,1]
<strong>Explanation:</strong> The array ans is formed as follows:
- ans = [nums[0],nums[1],nums[2],nums[0],nums[1],nums[2]]
- ans = [1,2,1,1,2,1]</pre>

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

<pre>
<strong>Input:</strong> nums = [1,3,2,1]
<strong>Output:</strong> [1,3,2,1,1,3,2,1]
<strong>Explanation:</strong> The array ans is formed as follows:
- ans = [nums[0],nums[1],nums[2],nums[3],nums[0],nums[1],nums[2],nums[3]]
- ans = [1,3,2,1,1,3,2,1]
</pre>

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

<ul>
	<li><code>n == nums.length</code></li>
	<li><code>1 &lt;= n &lt;= 1000</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 1000</code></li>
</ul>