Doubly Linked List

# include
<stdio.h>

# include <conio.h>

# include <alloc.h>

# include <stdlib.h>

struct link

{

struct
link *next,*pre;

char
name[25];

}*node,*h,*t,*t1;

main()

{

int
ch=1,tmp,op,ip,pno,co,i,fg=0;

char
pname[25],v[25];

node=NULL;

clrscr();

printf("\n\t\t\tDOUBLY
LINKED LIST\n\t\t\t~~~~~~ ~~~~~~ ~~~~");

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

printf("\n\tDoubly
linked list creation ");

printf("\n\tEnter
a string : ");

scanf("%s",node->name);

node->pre=NULL;

node->next=NULL;

h=node;

do

{

printf("\n\n1.Insert\n2.Delete\n3.Display\n4.Exit.");

printf("\n\tEnter
your choice : ");

scanf("%d",&op);

switch(op)

{

case 1:

printf("\n\t\tINSERT OPERATION\n");

printf("\n1. First\n2. Middle\n3.Last");

printf("\n\tEnter your choice : ");

scanf("%d",&ip);

switch(ip)

{

case 1:

t=(struct
link*)malloc(sizeof(
struct link));

printf("\n\tEnter the string : ");

scanf("%s",t->name);

t->pre=NULL;

t->next=h;

h=t;

node=t;

break;

case 2:

printf("\n\tEnter the position : ");

scanf("%d",&pno);

node=h;

co=0;

while(node!=NULL)

{

co=co+1;

node=node->next;

}

if(pno>co || pno<=0
|| pno==1)

{

printf("\n\tEnter the correct
position");

getch();

}

else

{

node=h;

i=2;

while(i<pno)

{

node=node->next;

i=i+1;

}

t=(struct
link*)malloc(sizeof(
struct link));

printf("\n\tEnter the string
: ");

scanf("%s",t->name);

t->next=node->next;

t->pre=node;

node->next=t;

node=node->next;

node->pre=t;

}

break;

case
3:

node=h;

while(node->next!=NULL)

node=node->next;

t=(struct
link*)malloc(sizeof(
struct link));

printf("\n\tEnter the string : ");

scanf("%s",t->name);

t->next=node->next;

t->pre=node;

node->next=t;

node=node->next;

node->pre=t;

break;

default :

printf("\n\n\t\tInvalid Choice.");

getch();

}

break;

case 2:

printf("\n\tDeletion");

printf("\n\tEnter the value to be
deleted : ");

scanf("%s",v);

node=h;

while(node!=NULL)

{

if(strcmp(node->name,v)==0)

{

fg=1;

if(node!=h && node->next!=NULL)

{

t->next=node->next;

node=node->next;

node->pre=t;

}

else
if(node==h && node->next!=NULL)

{

node=node->next;

node->pre=NULL;

h=node;

}

else
if(node==h && node->next==NULL)

{

node=NULL;

h=node;

}

else
if(node!=h && node->next==NULL)

{

t->next=NULL;

t=node;

}

printf("\n\t\tGiven value is deleted
");

getch();

break;

}

t=node;

node=node->next;

}

if(fg==0)

{

printf("\n\n\t\tThat value not in the list ");

getch();

}

break;

case 3:

printf("\n\tItems in the List\n\n\t\t");

node=h;

if(node==NULL )

printf("\n\tThe list is empty");

else

{

while(node->next!=NULL)

{

printf(" %s --> ",node->name);

node=node->next;

}

if(node->next==NULL)

printf("%s",node->name);

}

getch();

break;

case 4:

clrscr();

exit(0);

default:

printf("\n\n\n\t\t\tInvalid Choice.\n");

getch();

}

}while(ch!=4);

}