Reorder list halves

Join the first half and the reversed second half of a list into one list.

lists slicing reversal halves

Write a function `reorder_list(nums: list) -> list` that takes a list of values (any type, but tests use numbers/strings) and returns a new list formed by:

1. Taking the first half of `nums` — defined as the elements from index `0` up to (but not including) `len(nums) // 2`.
2. Taking the second half — the remaining elements from index `len(nums) // 2` to the end.
3. Reversing that second half.
4. Concatenating the first half and the reversed second half.

The original list must remain unchanged. If the list has fewer than 2 elements, return a copy of the original list (unchanged).

The function should work for lists of any length, including empty lists.

Constraints

0 <= len(nums) <= 1000
The list may contain integers or strings.
Time complexity: O(n), space complexity: O(n) for the output list.

Example

>>> reorder_list([1, 2, 3, 4, 5, 6])
[1, 2, 3, 6, 5, 4]
>>> reorder_list([1, 2, 3, 4, 5])
[1, 2, 5, 4, 3]
>>> reorder_list([])
[]
>>> reorder_list([1])
[1]

8 points ~10 min

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Hints

Find the middle index using integer division: `mid = len(nums) // 2`.

Slice the list into two parts: `first = nums[:mid]` and `second = nums[mid:]`.

Reverse the second part with `second[::-1]` or `reversed(second)`.

Concatenate the two parts and return the result.

Test Results

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