Concatenation of Array easy

Problem Statement

Given an integer array nums of length n, return an array of length 2n where the array is [nums, nums]. In other words, it should be the concatenation of the array nums with itself.

Example 1:

Input: nums = [1,2,1] Output: [1,2,1,1,2,1] Explanation: The array nums is concatenated with itself to produce the output [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 nums is concatenated with itself to produce the output [1,3,2,1,1,3,2,1].

Steps:

1. Create a new array: Initialize an empty array of length 2n, where n is the length of the input array nums. This will store the concatenated result.

2. Copy the original array: Copy the elements of nums into the first half of the new array.

3. Copy again: Copy the elements of nums again into the second half of the new array.

4. Return the new array: Return the new array containing the concatenated elements.

Explanation:

The problem directly asks for the concatenation of an array with itself. We can achieve this efficiently by creating a new array twice the size of the original and then populating it with the original array's contents twice. There's no need for complex algorithms; a simple copy operation suffices.

Code:

def getConcatenation(nums):
    """
    Concatenates an array with itself.

    Args:
        nums: The input integer array.

    Returns:
        A new array containing the concatenation of nums with itself.
    """
    n = len(nums)
    ans = [0] * (2 * n)  # Initialize an array of size 2n with zeros

    for i in range(n):
        ans[i] = nums[i]
        ans[i + n] = nums[i]

    return ans

# Example usage
nums1 = [1, 2, 1]
print(getConcatenation(nums1))  # Output: [1, 2, 1, 1, 2, 1]

nums2 = [1, 3, 2, 1]
print(getConcatenation(nums2))  # Output: [1, 3, 2, 1, 1, 3, 2, 1]

Complexity:

• Time Complexity: O(n), where n is the length of the input array. We iterate through the array twice (once to copy to the first half and once to copy to the second half).
• Space Complexity: O(n). We create a new array of size 2n to store the result.