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1929 - Concatenation of Array (Easy)

https://leetcode.com/problems/concatenation-of-array/

Problem Statement​

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: Iteration​

We need to look at nums two times to create the desired result. The simplest approach is to perform two for-loops in nums and copy the numbers to result .

Written by @heiheihang
def getConcatenation(self, nums: List[int]) -> List[int]:
        
        #initialize result
        result = []
        
        #first iteration of nums
        for i in range(len(nums)):
            result.append(nums[i])
        
        #second iteration of nums
        for i in range(len(nums)):
            result.append(nums[i])
        
        #return result
        return result