public class Solution
extends Object
1929 - Concatenation of Array\.
Easy
Given an integer array `nums` of length `n`, you want to create an array `ans` of length `2n` where `ans[i] == nums[i]` and `ans[i + n] == nums[i]` for `0 <= i < n` ( **0-indexed** ).
Specifically, `ans` is the **concatenation** of two `nums` arrays.
Return _the array_ `ans`.
**Example 1:**
**Input:** nums = [1,2,1]
**Output:** [1,2,1,1,2,1]
**Explanation:** 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]
**Example 2:**
**Input:** nums = [1,3,2,1]
**Output:** [1,3,2,1,1,3,2,1]
**Explanation:** 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]
**Constraints:**
* `n == nums.length`
* `1 <= n <= 1000`
* `1 <= nums[i] <= 1000`