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1929. Concatenation of Array

Question​

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

Approach​

  1. Append the vector again to the back of the original vector.

Solution​

class Solution {
public:
    vector<int> getConcatenation(vector<int>& nums) {
        int size = nums.size();
        for(int i = 0; i < size; i++){
            nums.push_back(nums[i]);
        }
        return nums;
    }
};