How to efficiently reverse a linked list?

Question

How do you efficiently reverse a linked list?

Sharp Talk · Answer

Absolutely! Efficiently reversing a linked list is a common task in programming and can be achieved using various algorithms. One efficient method is the iterative approach which involves traversing the list and reversing the pointers along the way. Here is a simple explanation of how this process works: 1. Start by defining three pointers: `current` `previous` and `next`. 2. Initialize `current` to the head of the linked list and `previous` to `null`. 3. While `current` is not `null` follow these steps: a. Save `current.next` in the `next` pointer. b. Point `current.next` to `previous`. c. Move `previous` to `current` and `current` to `next`. 4. Once the loop ends update the head of the linked list to the last `current` node which will be the new head of the reversed list. Here is a simple example in C# to demonstrate this iterative approach: public class ListNode { public int Value; public ListNode Next; public ListNode(int value) { Value = value; } } public class LinkedList { public ListNode ReverseLinkedList(ListNode head) { ListNode previous = null; ListNode current = head; while (current != null) { ListNode next = current.Next; current.Next = previous; previous = current; current = next; } return previous; } } By applying this iterative method you can efficiently reverse a linked list without the need for extra space making it a space-efficient solution. This operation is widely used in various applications such as handling data structures implementing algorithms and optimizing memory usage in software development.