Doubly linked list menu driven program in C

// C program for the all operations in

// the Doubly Linked List

#include <stdio.h>

#include <stdlib.h>

// Linked List Node

struct node {

int info;

struct node *prev, *next;

};

struct node* start = NULL;

// Function to traverse the linked list

void traverse()

{

// List is empty

if (start == NULL) {

printf("\nList is empty\n");

return;

}

// Else print the Data

struct node* temp;

temp = start;

while (temp != NULL) {

printf("Data = %d\n", temp->info);

temp = temp->next;

}

}

// Function to insert at the front

// of the linked list

void insertAtFront()

{

int data;

struct node* temp;

temp = (struct node*)malloc(sizeof(struct node));

printf("\nEnter number to be inserted: ");

scanf("%d", &data);

temp->info = data;

temp->prev = NULL;

// Pointer of temp will be

// assigned to start

temp->next = start;

start = temp;

}

// Function to insert at the end of

// the linked list

void insertAtEnd()

{

int data;

struct node *temp, *trav;

temp = (struct node*)malloc(sizeof(struct node));

temp->prev = NULL;

temp->next = NULL;

printf("\nEnter number to be inserted: ");

scanf("%d", &data);

temp->info = data;

temp->next = NULL;

trav = start;

// If start is NULL

if (start == NULL) {

start = temp;

}

// Changes Links

else {

while (trav->next != NULL)

trav = trav->next;

temp->prev = trav;

trav->next = temp;

}

}

// Function to insert at any specified

// position in the linked list

void insertAtPosition()

{

int data, pos, i = 1;

struct node *temp, *newnode;

newnode = malloc(sizeof(struct node));

newnode->next = NULL;

newnode->prev = NULL;

// Enter the position and data

printf("\nEnter position : ");

scanf("%d", &pos);

// If start==NULL,

if (start == NULL) {

start = newnode;

newnode->prev = NULL;

newnode->next = NULL;

}

// If position==1,

else if (pos == 1) {

// this is author method its correct but we can simply call insertAtfront() function for this special case

/* newnode->next = start;

newnode->next->prev = newnode;

newnode->prev = NULL;

start = newnode; */

// now this is improved by Jay Ghughriwala on geeksforgeeks

insertAtFront();

}

// Change links

else {

printf("\nEnter number to be inserted: ");

scanf("%d", &data);

newnode->info = data;

temp = start;

while (i < pos - 1) {

temp = temp->next;

i++;

}

newnode->next = temp->next;

newnode->prev = temp;

temp->next = newnode;

temp->next->prev = newnode;

}

}

// Function to delete from the front

// of the linked list

void deleteFirst()

{

struct node* temp;

if (start == NULL)

printf("\nList is empty\n");

else {

temp = start;

start = start->next;

if (start != NULL)

start->prev = NULL;

free(temp);

}

}

// Function to delete from the end

// of the linked list

void deleteEnd()

{

struct node* temp;

if (start == NULL)

printf("\nList is empty\n");

temp = start;

while (temp->next != NULL)

temp = temp->next;

if (start->next == NULL)

start = NULL;

else {

temp->prev->next = NULL;

free(temp);

}

}

// Function to delete from any specified

// position from the linked list

void deletePosition()

{

int pos, i = 1;

struct node *temp, *position;

temp = start;

// If DLL is empty

if (start == NULL)

printf("\nList is empty\n");

// Otherwise

else {

// Position to be deleted

printf("\nEnter position : ");

scanf("%d", &pos);

// If the position is the first node

if (pos == 1) {

deleteFirst(); // im,proved by Jay Ghughriwala on GeeksforGeeks

if (start != NULL) {

start->prev = NULL;

}

free(position);

return;

}

// Traverse till position

while (i < pos - 1) {

temp = temp->next;

i++;

}

// Change Links

position = temp->next;

if (position->next != NULL)

position->next->prev = temp;

temp->next = position->next;

// Free memory

free(position);

}

}

// Driver Code

int main()

{

int choice;

while (1) {

printf("\n\t1 To see list\n");

printf("\t2 For insertion at"

" starting\n");

printf("\t3 For insertion at"

" end\n");

printf("\t4 For insertion at "

"any position\n");

printf("\t5 For deletion of "

"first element\n");

printf("\t6 For deletion of "

"last element\n");

printf("\t7 For deletion of "

"element at any position\n");

printf("\t8 To exit\n");

printf("\nEnter Choice :\n");

scanf("%d", &choice);

switch (choice) {

case 1:

traverse();

break;

case 2:

insertAtFront();

break;

case 3:

insertAtEnd();

break;

case 4:

insertAtPosition();

break;

case 5:

deleteFirst();

break;

case 6:

deleteEnd();

break;

case 7:

deletePosition();

break;

case 8:

exit(1);

break;

default:

printf("Incorrect Choice. Try Again \n");

continue;

}

}

return 0;

}