Practice Reverse Nodes in k-Group

Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.

Hard#25

LeetCode Problem

Reverse Nodes in k-Group

Linked List Recursion

Problem Statement

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. Example 1: Example 2: Constraints: Follow-up: Can you solve the problem in O(1) extra memory space?

Source: Reverse Nodes in k-Group on LeetCode. Use the original task for its coding environment and submissions.

Examples

# Example 1

Input

head = [1,2,3,4,5], k = 2

Output

[2,1,4,3,5]

# Example 2

Input

head = [1,2,3,4,5], k = 3

Output

[3,2,1,4,5]

Constraints

The number of nodes in the list is n.

1 <= k <= n <= 5000

0 <= Node.val <= 1000

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