Reverse a Linked List in c++

A linked list is a data structure that consists of a chain of nodes, where each node contains a reference to the next node in the chain. In this article, we will be discussing how to reverse a linked list in C++.

Reversing a linked list is a common task in computer science and is often used in many different algorithms and data structures. The process of reversing a linked list involves iterating through the list and swapping the next pointer of each node with its previous pointer. This will result in the list being reversed in terms of the order of the nodes.

Before we dive into the code for reversing a linked list, let's first take a look at the basic structure of a linked list in C++. A linked list is typically implemented using a struct or class that defines the node, and a pointer to the next node in the list. Here is an example of a basic linked list structure in C++:

struct Node {
 int data; Node* next;
 };

In this example, the Node struct contains an integer data member and a pointer to the next node in the list. To create a linked list, we can create a head node, and then add additional nodes to the list by setting their next pointers to point to the previous node.

Now that we have a basic understanding of how a linked list is structured in C++, we can move on to the process of reversing the list. The basic algorithm for reversing a linked list is as follows:

  1. Create three pointers, prev, curr, and next.
  2. Initialize prev to NULL, curr to head, and next to head->next.
  3. Iterate through the list by moving curr to next and next to next->next.
  4. In each iteration, set curr->next to prev and update prev to curr.
  5. Finally, set head to prev.

Here is the C++ code for reversing a linked list using this algorithm:

void reverseList(Node*& head) {
 Node* prev = NULL;
 Node* curr = head;
 Node* next = head->next;
 while (curr != NULL) { 
 curr->next = prev; 
 prev = curr;
 curr = next;
 if (next != NULL) {
 next = next->next;
 } 
 }
 head = prev; }

In this code, we pass the head of the linked list as a reference to the reverseList function. We then initialize three pointers, prev, curr, and next. The prev pointer is initialized to NULL, the curr pointer is initialized to the head of the list, and the next pointer is initialized to the next node in the list.

We then iterate through the list using a while loop, where the condition is that the curr pointer is not equal to NULL. In each iteration, we set the next pointer of the curr node to the prev node, and then update the prev and curr pointers to the current node and the next node, respectively.

Finally, we set the head of the list to the prev pointer, which will now be the last node in the reversed list.

It is important to note that this algorithm has a time complexity of O(n) and a space complexity of O(1), where n is the number of nodes in the linked list. This makes it an efficient algorithm for reversing a linked list.

In conclusion, reversing a linked list in C++

Reverse a Linked List in c++