How to Reverse Nodes in K-Group in a Linked List?
Reversing nodes in groups of k in a linked list can be a common coding interview question, often asked to assess your understanding of linked lists and your ability to manipulate pointers effectively. This problem can appear complex at first, but through a structured approach, it can be tackled systematically.
The idea behind reversing nodes in k-groups is to take groups of k nodes from the linked list and reverse their order while keeping the overall structure intact. The core challenge lies in managing how you link these groups back together once they have been reversed.
Let’s illustrate this with an example. Consider a linked list represented as follows:
Html
If we are to reverse this list in groups of k = 2, the expected output should be:
Html
For k = 3, the output would be:
Html
To solve this problem, you can follow these steps:
-
Count the number of nodes: First, check how many nodes are in the linked list. This will help you know when you have enough nodes to form a group of k.
-
Reverse the nodes: While traversing the list, if there are at least k nodes remaining, reverse those k nodes.
-
Reconnect the reversed nodes: After reversing, connect the end of the reversed group to the start of the next group.
-
Handle the last group: If there are fewer than k nodes remaining, simply append them to the result without reversing.
Below is a Python implementation of this approach:
Python
In this solution, we create a helper function reverseLinkedList to handle the actual reversing of k nodes. The main function keeps track of previously processed nodes and efficiently connects the reversed segments back together. This code is structured for clarity, allowing anyone reviewing it to understand the logic behind the node manipulation.
