In the previous blog, we have seen the structure and properties of a Linked List. In this blog, we will discuss the types of a linked list and basic operations that can be performed on a linked list. Following are the types of linked list
A Singly-linked list is a collection of nodes linked together in a sequential way where each node of the singly linked list contains a data field and an address field that contains the reference of the next node. The structure of the node in the Singly Linked List is class Node { int data // variable to store the data of the node Node next // variable to store the address of the next node }The nodes are connected to each other in this form where the value of the next variable of the last node is NULL i.e. next = NULL, which indicates the end of the linked list. A Doubly Linked List contains an extra memory to store the address of the previous node, together with the address of the next node and data which are there in the singly linked list. So, here we are storing the address of the next as well as the previous nodes. The following is the structure of the node in the Doubly Linked List(DLL): class DLLNode { int val // variable to store the data of the node DLLNode prev // variable to store the address of the previous node DLLNode next // variable to store the address of the next node }The nodes are connected to each other in this form where the first node has prev = NULL and the last node has next = NULL. Advantages over Singly Linked List-
Disadvantages over Singly Linked List-
A circular linked list is either a singly or doubly linked list in which there are no NULL values. Here, we can implement the Circular Linked List by making the use of Singly or Doubly Linked List. In the case of a singly linked list, the next of the last node contains the address of the first node and in case of a doubly-linked list, the next of last node contains the address of the first node and prev of the first node contains the address of the last node. Advantages of a Circular linked list
Disadvantages of Circular linked list
We will see the various implementation of these operations on a singly linked list. Following is the structure of the node in a linked list: class Node{ int data // variable containing the data of the node Node next // variable containing the address of next node }The idea here is to step through the list from beginning to end. For example, we may want to print the list or search for a specific node in the list. The algorithm for traversing a list
There can be three cases that will occur when we are inserting a node in a linked list.
Insertion at the beginning Since there is no need to find the end of the list. If the list is empty, we make the new node as the head of the list. Otherwise, we we have to connect the new node to the current head of the list and make the new node, the head of the list. // function is returning the head of the singly linked-list Node insertAtBegin(Node head, int val) { newNode = new Node(val) // creating new node of linked list if(head == NULL) // check if linked list is empty return newNode else // inserting the node at the beginning { newNode.next = head return newNode } }Insertion at end We will traverse the list until we find the last node. Then we insert the new node to the end of the list. Note that we have to consider special cases such as list being empty. In case of a list being empty, we will return the updated head of the linked list because in this case, the inserted node is the first as well as the last node of the linked list. // the function is returning the head of the singly linked list Node insertAtEnd(Node head, int val) { if( head == NULL ) // handing the special case { newNode = new Node(val) head = newNode return head } Node temp = head // traversing the list to get the last node while( temp.next != NULL ) { temp = temp.next } newNode = new Node(val) temp.next = newNode return head }Insertion after a given node We are given the reference to a node, and the new node is inserted after the given node. void insertAfter(Node prevNode, int val) { newNode = new Node(val) newNode.next = prevNode.next prevNode.next = newNode }NOTE: If the address of the prevNode is not given, then you can traverse to that node by finding the data value. To delete a node from a linked list, we need to do these steps
In the deletion, there is a special case in which the first node is deleted. In this, we need to update the head of the linked list. // this function will return the head of the linked list Node deleteLL(Node head, Node del) { if(head == del) // if the node to be deleted is the head node { return head.next // special case for the first Node } Node temp = head while( temp.next != NULL ) { if(temp.next == del) // finding the node to be deleted { temp.next = temp.next.next delete del // free the memory of that Node return head } temp = temp.next } return head // if no node matches in the Linked List }To search any value in the linked list, we can traverse the linked list and compares the value present in the node. bool searchLL(Node head, int val) { Node temp = head // creating a temp variable pointing to the head of the linked list while( temp != NULL) // traversing the list { if( temp.data == val ) return true temp = temp.next } return false }To update the value of the node, we just need to set the data part to the new value. Below is the implementation in which we had to update the value of the first node in which data is equal to val and we have to set it to newVal. void updateLL(Node head, int val, int newVal) { Node temp = head while(temp != NULL) { if( temp.data == val) { temp.data = newVal return } temp = temp.next } }Happy coding! Enjoy Algorithms. |