Concatenation of Array

I did this Leetcode problem. It is fairly straightforward and easy but my first attempt was not the most optimal.

class Solution(object):
    def getConcatenation(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        ans = list(nums)
        for i in nums:
            ans.append(i)
        return ans

This was my first attempt. I shallow copied the nums array to ans and then I appended nums to the end of ans. While it is still O(n), it wasn’t the fastest solution.

class Solution:
    def getConcatenation(self, nums):
        ans = []
        for i in range(2):
            for n in nums:
                ans.append(n)
        return ans

This solution is much more elegant because we can repeat nums 3 times very easily with this code. The outer for loop is constant time since we are only doing it two times. Thus making this solution O(n) time.