Describe a node of double linked list. Write an algorithm to deletthe last node of a non-emoty double linked list?
Answers
In computer science, a doubly linked list is a linked data structure that consists of a set of sequentially linked records called nodes. Each node contains three fields: two link fields and one data field.
Explanation:
After deletion of head node.
After deletion of middle node.
After deletion of last node.
All three mentioned cases can be handled in two steps if the pointer of the node to be deleted and the head pointer is known.
If the node to be deleted is the head node then make the next node as head.
If a node is deleted, connect the next and previous node of the deleted node.
Algorithm
Let the node to be deleted be del.
If node to be deleted is head node, then change the head pointer to next current head.
if headnode == del then
headnode = del.nextNode
Set next of previous to del, if previous to del exists.
if del.nextNode != none
del.nextNode.previousNode = del.previousNode
Set prev of next to del, if next to del exists.
if del.previousNode != none
del.nextNode.nextNode = del.next
// C++ program to delete a node from
// Doubly Linked List
#include <bits/stdc++.h>
using namespace std;
/* a node of the doubly linked list */
class Node
{
public:
int data;
Node* next;
Node* prev;
};
/* Function to delete a node in a Doubly Linked List.
head_ref --> pointer to head node pointer.
del --> pointer to node to be deleted. */
void deleteNode(Node** head_ref, Node* del)
{
/* base case */
if (*head_ref == NULL || del == NULL)
return;
/* If node to be deleted is head node */
if (*head_ref == del)
*head_ref = del->next;
/* Change next only if node to be
deleted is NOT the last node */
if (del->next != NULL)
del->next->prev = del->prev;
/* Change prev only if node to be
deleted is NOT the first node */
if (del->prev != NULL)
del->prev->next = del->next;
/* Finally, free the memory occupied by del*/
free(del);
return;
}
/* UTILITY FUNCTIONS */
/* Function to insert a node at the
beginning of the Doubly Linked List */
void push(Node** head_ref, int new_data)
{
/* allocate node */
Node* new_node = new Node();
/* put in the data */
new_node->data = new_data;
/* since we are adding at the beginning,
prev is always NULL */
new_node->prev = NULL;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* change prev of head node to new node */
if ((*head_ref) != NULL)
(*head_ref)->prev = new_node;
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* Function to print nodes in a given doubly linked list
This function is same as printList() of singly linked list */
void printList(Node* node)
{
while (node != NULL)
{
cout << node->data << " ";
node = node->next;
}
}
/* Driver code*/
int main()
{
/* Start with the empty list */
Node* head = NULL;
/* Let us create the doubly linked list 10<->8<->4<->2 */
push(&head, 2);
push(&head, 4);
push(&head, 8);
push(&head, 10);
cout << "Original Linked list ";
printList(head);
/* delete nodes from the doubly linked list */
deleteNode(&head, head); /*delete first node*/
deleteNode(&head, head->next); /*delete middle node*/
deleteNode(&head, head->next); /*delete last node*/
/* Modified linked list will be NULL<-8->NULL */
cout << "\nModified Linked list ";
printList(head);
return 0;
}
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