What is the optimal time complexity of solving Reverse Nodes In K Group?

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 Reverse Nodes In K Group?

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 Reverse Nodes In K Group?

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 Reverse Nodes In K Group?

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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Reverse Nodes In K Group

Learn how to solve the 'Reverse Nodes In K Group' problem. This detailed resource details brute force and optimized approaches.

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Problem Statement

Easy

Given the head of a linked list, reverse the nodes of the list k at a time, and return the modified list.

k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k then left-out nodes, in the end, should remain as it is.

You may not alter the values in the list's nodes, only nodes themselves may be changed.

The linked list is represented as a Python list. Implement a function reverseKGroup(head: list, k: int) -> list.

Constraints

•The number of nodes in the list is n
•1 <= k <= n <= 5000
•0 <= Node.val <= 1000

Examples

Example 1

Input

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

Output

[2,1,4,3,5]

Explanation

Reverse in groups of 2: [1,2] becomes [2,1], [3,4] becomes [4,3], and [5] stays as is.

Example 2

Input

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

Output

[3,2,1,4,5]

Explanation

Reverse in groups of 3: [1,2,3] becomes [3,2,1], and [4,5] has fewer than 3 nodes so it stays.

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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