25. Reverse Nodes in k-Group
Reverse Nodes in k-Group (LeetCode 25) is a Hard Data Structures and Algorithms interview problem you can solve, run and submit on Thita.ai. It belongs to the Linked List Manipulation Patterns pattern, in the In-place Reversal subpattern.
How to solve Reverse Nodes in k-Group
Reverse Nodes in k-Group is a In-Place Linked List Reversal problem, part of Linked List Manipulation Patterns. Master in-place linked list reversal including full reversal, partial reversal, and k-group reversal techniques.
Work towards the solution in these steps:
- Consider the problem as a series of smaller linked list segments of size k that need to be reversed individually.
- Focus on how to traverse the linked list in chunks of k nodes and identify when you have enough nodes to reverse.
- Think about reversing each k-sized segment in place by manipulating the next pointers without changing node values.
The reference solution runs in O(n) time and O(1) space.
The Reverse Nodes in k-Group solution and editorial walks through the full approach with reference code.
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:
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
Follow-up: Can you solve the problem in O(1) extra memory space?
Topics and companies
Topics: Linked List, Recursion.
Reported in interviews at Amazon, Microsoft, Apple, ByteDance, Facebook, Google.
How to practise Reverse Nodes in k-Group on Thita.ai
Starter code is provided in C, C#, C++, Go, Java, JavaScript and Python. Your solution runs against 5 test cases for this problem, with the AI coach available for a hint when you are stuck rather than a finished answer. The reference solution runs in O(n) time and O(1) space.
Open Reverse Nodes in k-Group in the code editor, or read the Reverse Nodes in k-Group editorial for a worked solution with its approach and complexity analysis.
Where Reverse Nodes in k-Group sits in the DSA pattern sheet
- Linked List Manipulation Patterns pattern guide
- In-place Reversal subpattern
- The full DSA patterns sheet
Problems related to Reverse Nodes in k-Group
Other problems that use the same In-place Reversal and Linked List Manipulation Patterns techniques:
- Palindrome Linked List — Easy, same subpattern
- Remove Duplicates from Sorted List — Easy, same subpattern
- Remove Duplicates from Sorted List II — Medium, same subpattern
- Reverse Linked List — Easy, same subpattern
- Reverse Linked List II — Medium, same subpattern
- Add Two Numbers — Medium, same pattern
Reverse Nodes in k-Group FAQ
What is the LeetCode number of Reverse Nodes in k-Group?
Reverse Nodes in k-Group is LeetCode problem 25, rated Hard.
What pattern is used to solve Reverse Nodes in k-Group?
Reverse Nodes in k-Group is a In-Place Linked List Reversal problem. It belongs to the Linked List Manipulation Patterns pattern, in the In-place Reversal subpattern.
What is the time complexity of Reverse Nodes in k-Group?
The reference solution runs in O(n) time and O(1) space.
Which companies ask Reverse Nodes in k-Group?
Reverse Nodes in k-Group has been reported in interviews at Amazon, Microsoft, Apple, ByteDance, Facebook, Google.