1929. Concatenation of Array

Problem

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

Solution (Java)

class Solution {
    public int[] getConcatenation(int[] nums) {
        int[] result = new int[nums.length * 2];
        System.arraycopy(nums, 0, result, 0, nums.length);
        int i = nums.length;
        for (int j = 0; i < result.length && j < nums.length; i++, j++) {
            result[i] = nums[j];
        }
        return result;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).