##### Welcome to Subscribe On Youtube

Formatted question description: https://leetcode.ca/all/1929.html

# 1929. Concatenation of Array

Easy

## Description

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

Get the length of nums as n. Create an array ans of length n * 2. Then for each i from 0 to n - 1, let ans[i] = ans[i + n] = nums[i]. Finally, return ans.

• class Solution {
public int[] getConcatenation(int[] nums) {
int n = nums.length;
int[] concat = new int[n * 2];
for (int i = 0; i < n; i++) {
concat[i] = nums[i];
concat[i + n] = nums[i];
}
return concat;
}
}

############

class Solution {
public int[] getConcatenation(int[] nums) {
int n = nums.length;
int[] ans = new int[n << 1];
for (int i = 0; i < n << 1; ++i) {
ans[i] = nums[i % n];
}
return ans;
}
}

• // OJ: https://leetcode.com/problems/concatenation-of-array/
// Time: O(N)
// Space: O(1)
class Solution {
public:
vector<int> getConcatenation(vector<int>& A) {
vector<int> ans(A);
int N = A.size();
for (int i = 0; i < N; ++i) ans.push_back(A[i]);
return ans;
}
};

• class Solution:
def getConcatenation(self, nums: List[int]) -> List[int]:
return nums + nums

############

# 1929. Concatenation of Array
# https://leetcode.com/problems/concatenation-of-array/

class Solution:
def getConcatenation(self, nums: List[int]) -> List[int]:
return nums + nums


• func getConcatenation(nums []int) []int {
return append(nums, nums...)
}

• function getConcatenation(nums: number[]): number[] {
return [...nums, ...nums];
}


• /**
* @param {number[]} nums
* @return {number[]}
*/
var getConcatenation = function (nums) {
let ans = nums.slice();
ans.splice(nums.length, 0, ...nums);
return ans;
};


• impl Solution {
pub fn get_concatenation(nums: Vec<i32>) -> Vec<i32> {
nums.repeat(2)
}
}