C Program to Implement a Doubly Linked List & provide Insertion, Deletion & Display Operations

This C Program implement a doubly linked list & provide insertion, deletion & display operations. Doubly linked list is a linked data
structure that consists of a set of sequentially linked records called nodes. Each node contains two fields, called links, that are references to the previous and to the next node in the sequence of nodes. The beginning and ending nodes’ previous and next
links, respectively, point to some kind of terminator, typically a sentinel node or null, to facilitate traversal of the list. Here we need to preform insertion, deletion and display all the modes of given doubly linked list.

Here is source code of the C Program to implement a doubly linked list & provide insertion, deletion & display operations. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

/*
* C Program to Implement a Doubly Linked List & provide Insertion, Deletion & Display Operations
*/
#include <stdio.h>
#include <stdlib.h>

struct node
{
struct node *prev;
int n;
struct node *next;
}*h,*temp,*temp1,*temp2,*temp4;

void insert1();
void insert2();
void insert3();
void traversebeg();
void traverseend(int);
void sort();
void search();
void update();
void delete();

int count = 0;

void main()
{
int ch;

h = NULL;
temp = temp1 = NULL;

printf("\n 1 - Insert at beginning");
printf("\n 2 - Insert at end");
printf("\n 3 - Insert at position i");
printf("\n 4 - Delete at i");
printf("\n 5 - Display from beginning");
printf("\n 6 - Display from end");
printf("\n 7 - Search for element");
printf("\n 8 - Sort the list");
printf("\n 9 - Update an element");
printf("\n 10 - Exit");

while (1)
{
printf("\n Enter choice : ");
scanf("%d", &ch);
switch (ch)
{
case 1:
insert1();
break;
case 2:
insert2();
break;
case 3:
insert3();
break;
case 4:
delete();
break;
case 5:
traversebeg();
break;
case 6:
temp2 = h;
if (temp2 == NULL)
printf("\n Error : List empty to display ");
else
{
printf("\n Reverse order of linked list is : ");
traverseend(temp2->n);
}
break;
case 7:
search();
break;
case 8:
sort();
break;
case 9:
update();
break;
case 10:
exit(0);
default:
printf("\n Wrong choice menu");
}
}
}

/* TO create an empty node */
void create()
{
int data;

temp =(struct node *)malloc(1*sizeof(struct node));
temp->prev = NULL;
temp->next = NULL;
printf("\n Enter value to node : ");
scanf("%d", &data);
temp->n = data;
count++;
}

/*  TO insert at beginning */
void insert1()
{
if (h == NULL)
{
create();
h = temp;
temp1 = h;
}
else
{
create();
temp->next = h;
h->prev = temp;
h = temp;
}
}

/* To insert at end */
void insert2()
{
if (h == NULL)
{
create();
h = temp;
temp1 = h;
}
else
{
create();
temp1->next = temp;
temp->prev = temp1;
temp1 = temp;
}
}

/* To insert at any position */
void insert3()
{
int pos, i = 2;

printf("\n Enter position to be inserted : ");
scanf("%d", &pos);
temp2 = h;

if ((pos < 1) || (pos >= count + 1))
{
printf("\n Position out of range to insert");
return;
}
if ((h == NULL) && (pos != 1))
{
printf("\n Empty list cannot insert other than 1st position");
return;
}
if ((h == NULL) && (pos == 1))
{
create();
h = temp;
temp1 = h;
return;
}
else
{
while (i < pos)
{
temp2 = temp2->next;
i++;
}
create();
temp->prev = temp2;
temp->next = temp2->next;
temp2->next->prev = temp;
temp2->next = temp;
}
}

/* To delete an element */
void delete()
{
int i = 1, pos;

printf("\n Enter position to be deleted : ");
scanf("%d", &pos);
temp2 = h;

if ((pos < 1) || (pos >= count + 1))
{
printf("\n Error : Position out of range to delete");
return;
}
if (h == NULL)
{
printf("\n Error : Empty list no elements to delete");
return;
}
else
{
while (i < pos)
{
temp2 = temp2->next;
i++;
}
if (i == 1)
{
if (temp2->next == NULL)
{
printf("Node deleted from list");
free(temp2);
temp2 = h = NULL;
return;
}
}
if (temp2->next == NULL)
{
temp2->prev->next = NULL;
free(temp2);
printf("Node deleted from list");
return;
}
temp2->next->prev = temp2->prev;
if (i != 1)
temp2->prev->next = temp2->next;    /* Might not need this statement if i == 1 check */
if (i == 1)
h = temp2->next;
printf("\n Node deleted");
free(temp2);
}
count--;
}

/* Traverse from beginning */
void traversebeg()
{
temp2 = h;

if (temp2 == NULL)
{
printf("List empty to display \n");
return;
}
printf("\n Linked list elements from begining : ");

while (temp2->next != NULL)
{
printf(" %d ", temp2->n);
temp2 = temp2->next;
}
printf(" %d ", temp2->n);
}

/* To traverse from end recursively */
void traverseend(int i)
{
if (temp2 != NULL)
{
i = temp2->n;
temp2 = temp2->next;
traverseend(i);
printf(" %d ", i);
}
}

/* To search for an element in the list */
void search()
{
int data, count = 0;
temp2 = h;

if (temp2 == NULL)
{
printf("\n Error : List empty to search for data");
return;
}
printf("\n Enter value to search : ");
scanf("%d", &data);
while (temp2 != NULL)
{
if (temp2->n == data)
{
printf("\n Data found in %d position",count + 1);
return;
}
else
temp2 = temp2->next;
count++;
}
printf("\n Error : %d not found in list", data);
}

/* To update a node value in the list */
void update()
{
int data, data1;

printf("\n Enter node data to be updated : ");
scanf("%d", &data);
printf("\n Enter new data : ");
scanf("%d", &data1);
temp2 = h;
if (temp2 == NULL)
{
printf("\n Error : List empty no node to update");
return;
}
while (temp2 != NULL)
{
if (temp2->n == data)
{

temp2->n = data1;
traversebeg();
return;
}
else
temp2 = temp2->next;
}

printf("\n Error : %d not found in list to update", data);
}

/* To sort the linked list */
void sort()
{
int i, j, x;

temp2 = h;
temp4 = h;

if (temp2 == NULL)
{
printf("\n List empty to sort");
return;
}

for (temp2 = h; temp2 != NULL; temp2 = temp2->next)
{
for (temp4 = temp2->next; temp4 != NULL; temp4 = temp4->next)
{
if (temp2->n > temp4->n)
{
x = temp2->n;
temp2->n = temp4->n;
temp4->n = x;
}
}
}
traversebeg();
}

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$ gcc pgm1.c
$ ./a.out

1 - Insert at beginning
2 - Insert at end
3 - Insert at position i
4 - Delete at i
5 - Display from beginning
6 - Display from end
7 - Search for element
8 - Sort the list
9 - Update an element
10 - Exit
Enter choice : 1

Enter value to node : 10

Enter choice : 2

Enter value to node : 50

Enter choice : 4

Enter position to be deleted : 1

Node deleted
Enter choice : 1

Enter value to node : 34

Enter choice : 3

Enter position to be inserted : 2

Enter value to node : 13

Enter choice : 4

Enter position to be deleted : 4

Error : Position out of range to delete
Enter choice : 1

Enter value to node : 15

Enter choice : 1

Enter value to node : 67

Enter choice : 3

Enter position to be inserted : 2

Enter value to node : 34

Enter choice : 4

Enter position to be deleted : 3

Node deleted
Enter choice : 7

Enter value to search : 15

Error : 15 not found in list
Enter choice : 8

Linked list elements from begining :  13  34  34  50  67
Enter choice : 9

Enter node data to be updated : 45

Enter new data : 89

Error : 45 not found in list to update
Enter choice : 9

Enter node data to be updated : 50

Enter new data : 90
Enter choice : 5

Linked list elements from begining :  13  34  34  90  67
Enter choice : 6

Reverse order of linked list is :  67  90  34  34  13
Enter choice : 7

Enter value to search : 90

Data found in 4 position
Enter choice : 8

Linked list elements from begining :  13  34  34  67  90
Enter choice : 7

Enter value to search : 90

Data found in 5 position
Enter choice : 9

Enter node data to be updated : 34

Enter new data : 56

Linked list elements from begining :  13  56  34  67  90
Enter choice : 10