Write a C program to create a doubly linked list and delete a node from beginning, end or at any position of the linked list. How to delete a node from beginning of a doubly linked list. How to delete a node from end of a doubly linked list. How to delete a node from any position of a doubly linked list in C. Algorithm to delete a node from doubly linked list.
Required knowledge
Basic C programming, Functions, Dynamic memory allocation, Doubly linked list
Algorithm to delete node from beginning of a doubly linked list
Algorithm to delete node from beginning
%% Input: head {Pointer to first node of the linked list}
Begin:
If (head == NULL) then
write ('Can't delete from an empty list')
End if
Else then
toDelete ← head;
head ← head.next;
head.prev ← NULL;
unalloc (toDelete)
write ('Successfully deleted first node from the list')
End if
EndAlgorithm to delete node from end of a doubly linked list
Algorithm to delete node from end
%% Input: last {Pointer to last node of the linked list}
Begin:
If (last == NULL) then
write ('Can't delete from an empty list')
End if
Else then
toDelete ← last;
last ← last.prev;
last.next ← NULL;
unalloc (toDelete)
write ('Successfully deleted last node from the list')
End if
EndAlgorithm to delete node from any position of a doubly linked list
Algorithm to delete node from any position
%% Input : head {Pointer to the first node of the list}
last {Pointer to the last node of the list}
N {Position to be deleted from list}
Begin:
current ← head;
For i ← 1 to N and current != NULL do
current ← current.next;
End for
If (N == 1) then
deleteFromBeginning()
End if
Else if (current == last) then
deleteFromEnd()
End if
Else if (current != NULL) then
current.prev.next ← current.next
If (current.next != NULL) then
current.next.prev ← current.prev;
End if
unalloc (current)
write ('Node deleted successfully from ', N, ' position')
End if
Else then
write ('Invalid position')
End if
EndSteps to delete node from any position of a doubly linked list
Let us suppose that we want to delete node from 2nd position.
- Traverse to Nth node of the linked list, lets say a pointer current points to Nth node in our case 2 node.
- Link the node behind current node with the node ahead of current node, which means now the N-1th node will point to N+1th node of the list. Which can be implemented as current->prev->next = current->next.
- If N+1th node is not NULL then link the N+1th node with N-1th node i.e. now the previous address field of N+1th node will point to N-1th node. Which can be implemented as current->next->prev = current->prev.
- Finally delete the current node from memory and you are done.
Program to delete a node from doubly linked list
/**
* C program to delete a node from Doubly linked list
*/
#include <stdio.h>
#include <stdlib.h>
/*
* Basic structure of Node
*/
struct node {
int data;
struct node * prev;
struct node * next;
}*head, *last;
/*
* Functions used in this program
*/
void createList(int n);
void displayList();
void deleteFromBeginning();
void deleteFromEnd();
void deleteFromN(int position);
int main()
{
int n, data, choice=1;
head = NULL;
last = NULL;
/*
* Run forever until user chooses 0
*/
while(choice != 0)
{
printf("============================================\n");
printf("DOUBLY LINKED LIST PROGRAM\n");
printf("============================================\n");
printf("1. Create List\n");
printf("2. Delete node - from beginning\n");
printf("3. Delete node - from end\n");
printf("4. Delete node - from N\n");
printf("5. Display list\n");
printf("0. Exit\n");
printf("--------------------------------------------\n");
printf("Enter your choice : ");
scanf("%d", &choice);
switch(choice)
{
case 1:
printf("Enter the total number of nodes in list: ");
scanf("%d", &n);
createList(n);
break;
case 2:
deleteFromBeginning();
break;
case 3:
deleteFromEnd();
break;
case 4:
printf("Enter the node position which you want to delete: ");
scanf("%d", &n);
deleteFromN(n);
break;
case 5:
displayList();
break;
case 0:
break;
default:
printf("Error! Invalid choice. Please choose between 0-5");
}
printf("\n\n\n\n\n");
}
return 0;
}
/**
* Creates a doubly linked list of n nodes.
* @n Number of nodes to be created
*/
void createList(int n)
{
int i, data;
struct node *newNode;
if(n >= 1)
{
/*
* Creates and links the head node
*/
head = (struct node *)malloc(sizeof(struct node));
printf("Enter data of 1 node: ");
scanf("%d", &data);
head->data = data;
head->prev = NULL;
head->next = NULL;
last = head;
/*
* Create and link rest of the n-1 nodes
*/
for(i=2; i<=n; i++)
{
newNode = (struct node *)malloc(sizeof(struct node));
printf("Enter data of %d node: ", i);
scanf("%d", &data);
newNode->data = data;
newNode->prev = last; // Link new node with the previous node
newNode->next = NULL;
last->next = newNode; // Link previous node with the new node
last = newNode; // Make new node as last node
}
printf("\nDOUBLY LINKED LIST CREATED SUCCESSFULLY\n");
}
}
/**
* Display the content of the list from beginning to end
*/
void displayList()
{
struct node * temp;
int n = 1;
if(head == NULL)
{
printf("List is empty.\n");
}
else
{
temp = head;
printf("DATA IN THE LIST:\n");
while(temp != NULL)
{
printf("DATA of %d node = %d\n", n, temp->data);
n++;
/* Move the current pointer to next node */
temp = temp->next;
}
}
}
/**
* Delete or remove the first node of the doubly linked list
*/
void deleteFromBeginning()
{
struct node * toDelete;
if(head == NULL)
{
printf("Unable to delete. List is empty.\n");
}
else
{
toDelete = head;
head = head->next; // Move head pointer to 2 node
if (head != NULL)
head->prev = NULL; // Remove the link to previous node
free(toDelete); // Delete the first node from memory
printf("SUCCESSFULLY DELETED NODE FROM BEGINNING OF THE LIST.\n");
}
}
/**
* Delete or remove the last node of the doubly linked list
*/
void deleteFromEnd()
{
struct node * toDelete;
if(last == NULL)
{
printf("Unable to delete. List is empty.\n");
}
else
{
toDelete = last;
last = last->prev; // Move last pointer to 2nd last node
if (last != NULL)
last->next = NULL; // Remove link to of 2nd last node with last node
free(toDelete); // Delete the last node
printf("SUCCESSFULLY DELETED NODE FROM END OF THE LIST.\n");
}
}
/**
* Delete node from any position in the doubly linked list
*/
void deleteFromN(int position)
{
struct node *current;
int i;
current = head;
for(i=1; i<position && current!=NULL; i++)
{
current = current->next;
}
if(position == 1)
{
deleteFromBeginning();
}
else if(current == last)
{
deleteFromEnd();
}
else if(current != NULL)
{
current->prev->next = current->next;
current->next->prev = current->prev;
free(current); // Delete the n node
printf("SUCCESSFULLY DELETED NODE FROM %d POSITION.\n", position);
}
else
{
printf("Invalid position!\n");
}
}============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 1 Enter the total number of nodes in list: 5 Enter data of 1 node: 10 Enter data of 2 node: 20 Enter data of 3 node: 30 Enter data of 4 node: 40 Enter data of 5 node: 50DOUBLY LINKED LIST CREATED SUCCESSFULLY ============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 5 DATA IN THE LIST: DATA of 1 node = 10 DATA of 2 node = 20 DATA of 3 node = 30 DATA of 4 node = 40 DATA of 5 node = 50 ============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 2 SUCCESSFULLY DELETED NODE FROM BEGINNING OF THE LIST. ============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 5 DATA IN THE LIST: DATA of 1 node = 20 DATA of 2 node = 30 DATA of 3 node = 40 DATA of 4 node = 50 ============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 3 SUCCESSFULLY DELETED NODE FROM END OF THE LIST. ============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 5 DATA IN THE LIST: DATA of 1 node = 20 DATA of 2 node = 30 DATA of 3 node = 40 ============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 4 Enter the node position which you want to delete: 2 SUCCESSFULLY DELETED NODE FROM 2 POSITION. ============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 5 DATA IN THE LIST: DATA of 1 node = 20 DATA of 2 node = 40 ============================================ DOUBLY LINKED LIST PROGRAM ============================================ 1. Create List 2. Delete node - from beginning 3. Delete node - from end 4. Delete node - from N 5. Display list 0. Exit -------------------------------------------- Enter your choice : 0