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.

Create an array to hold the concatenated array. The goal is to repeat the array twice in a new array. Therefore, it is easy to repeat as so: ans = [nums, nums] = [nums[0], nums[1], nums[2], ..., nums[0], nums[1], nums[2], ...]

1. Create an array that has size nums.size x 2

2. Run through every number in nums and add it twice.

   1. First add to [i]

   2. Then add to [i+nums.size]

      1. ans[i] = nums[i]

      2. ans[i+nums.size] = nums[i]

For example: nums = [1, 2, 3]

ans = a new int array of size 2*3 = 6

(At iteration i = 0) ans = [1, 0, 0, 1, 0, 0] (int arrays are initialized with 0s)

(At iteration i = 1) ans = [1, 2, 0, 1, 2, 0]

(At iteration i = 2) ans = [1, 2, 3, 1, 2, 3]