Reverse K Nodes in a Linked List

 

A linked list is a common data structure used in computer science and programming, consisting of a sequence of nodes, each containing a value and a pointer to the next node in the list. However, there may be times when it is necessary to reverse a portion of the linked list, known as reverse K nodes in a linked list.

In this article, we will discuss the concept of reverse K nodes in a linked list and its implementation in C++. We will begin by understanding the basic concept of linked lists and the need for reversing nodes in a linked list.

A linked list is a linear collection of data elements called nodes, where each node points to the next node in the list. The last node in the list, known as the tail, points to null, indicating the end of the list. The first node in the list, known as the head, does not have a previous node.

The main advantage of linked lists over arrays is their dynamic nature, which allows for easy insertion and deletion of elements. However, linked lists can also be reversed, which can be useful in certain algorithms and programming tasks.

Reverse K nodes in a linked list refers to reversing a specific portion of the linked list, rather than the entire list. The portion to be reversed is determined by the value of K, which represents the number of nodes to be reversed.

For example, if a linked list has a total of 8 nodes and K is set to 3, the first 3 nodes of the list will be reversed, resulting in a new list with the last 3 nodes as the first 3 nodes.

The process of reversing K nodes in a linked list can be implemented using a combination of pointers and iterators. The following is an example of the implementation of reverse K nodes in a linked list in C++:

//function to reverse K nodes in a linked list
 
void reverseKNodes(int k)
{
 //create a pointer to the head of the list 
 Node *current = head; 
 //create a pointer to the previous node 
 Node *prev = nullptr; 
 //create a pointer to the next node 
 Node *next = nullptr; 
 //create a counter to keep track of the number of nodes reversed 
 int count = 0;
 //iterate through the list until the end is reached or K nodes have been reversed
     
while (current != nullptr && count < k)
    { 
 //store the next node in the list 
 next = current->next;
 //reverse the current node by pointing it to the previous node 
 current->next = prev;
 //update the previous node to be the current node 
 prev = current;
 //update the current node to be the next node 
 current = next;
 //increment the counter
        count++;
 }
    //update the head of the list to be the last node reversed 
 head = prev; 
}

In this example, the reverseKNodes() function takes in an integer value, k, as a parameter. The function first creates pointers for the current node, previous node, and next node, as well as a counter for the number of nodes reversed.

The function then uses a while loop to iterate through the list until the end of the list is reached or K nodes have been reversed. Within the while loop, the next node in the list is stored, the current node is reversed by pointing it to the previous node, and the pointers for the previous and current nodes are updated.

The function then updates the head of the list to be the