What is the optimal time complexity of solving Fold Linked List?

The optimized solution achieves a time complexity of O(n) by using sorting, mathematical shortcuts, or hash table lookups.

What is the auxiliary space complexity for Fold Linked List?

The space complexity is O(1) since we only use a minimal/constant amount of extra memory for tracking variables (or auxiliary space if dynamic structures are allocated).

What are the typical edge cases we must handle in Fold Linked List?

Key edge cases include empty collections, negative or large bounds causing integer overflow, arrays with only one element, or inputs where target criteria are not met.

How can we optimize the brute force approach for Fold Linked List?

Brute force methods often inspect all possible combinations. We optimize this by sorting the input list to enable binary search, or tracking processed items in a set to avoid redundant nested loop lookups.

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DSA SectionEasy

Fold Linked List

Learn how to solve the 'Fold Linked List' problem. This detailed resource details brute force and optimized approaches.

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Problem Statement

Easy

Write a function fold_list(arr) that represents a singly linked list as a Python list arr and returns the folded list. Folding a list L0 -> L1 -> ... -> Ln-1 -> Ln results in L0 -> Ln -> L1 -> Ln-1 -> L2 -> Ln-2 ....

Constraints

•0 <= len(arr) <= 1000
•-1000 <= arr[i] <= 1000

Examples

Example 1

Input

arr = [1, 2, 3, 4, 5]

Output

[1, 5, 2, 4, 3]

Explanation

The nodes are reordered by interleaving the first, last, second, second-to-last nodes, etc.

Example 2

Input

arr = [1, 2, 3, 4]

Output

[1, 4, 2, 3]

Need a Hint?

Analyze the input constraints. Try sorting first (O(n log n)) or using a hash map/set to track seen elements in O(n) time.

Edge Cases to Watch

Empty list or null input variables
Single item lists/arrays
Extremely large input bounds causing integer or stack overflow

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