Program to demonstrate linked list operations

# include
# include
# include "malloc.h"
struct node
{
int data;
struct node *link;
};

void main()
{
int a=111,b=2,c=3,will,wish,num;
struct node *ptr,*ptr2,*result,*temp;
void add(struct node **,int );
struct node * search(struct node *);
void display(struct node *);
void invert(struct node *);
void del(struct node *,int);
struct node * concat(struct node *,struct node *);
ptr=NULL;
ptr2=NULL;
result=NULL; //result for storing the result of concatenation
clrscr();
will=1;

while(will==1)
{
printf("

Main Menu
1. Add element
2.Delete element
3.Search element
4Linked List concatenation
5.Invert linked list
6. Display elements
Please enter the choice");
scanf("%d",&wish);
switch(wish)
{
case 1:
printf("
Enter the element you want to add   ");
scanf("%d",&num);
add(&ptr,num);
display(ptr);
break;
case 2:
printf("
Enter the element to delete ");
scanf("%d",&num);
del(ptr,num);
break;
case 3:
printf("
 Now demonstrating search ");
temp = search(ptr);
printf("
Address of first occurence is  %u ",temp);
break;
case 4:
/* Inputs given internally for demo only */
printf(" Now demonstrating linked list concatenation
 Press any key to continue...");
add(&ptr2,2);
add(&ptr2,4);
add(&ptr2,6);
getch();
printf("

 Displaying second Linked List


");
display(ptr2);
getch();
result = concat(ptr,ptr2);
clrscr();
printf("



Now Displaying the result of concatenation");
display(result);
getch();
break;
case 5:

printf("
 Inverting the list ...
Press any key to continue...");
invert(ptr);
break;
case 6:
display(ptr);
break;
default:
printf("

 Illegal choice

");
}
printf("
 DO you want to continue ( press 1 for yes ");
scanf("%d",&will);
} //end of while
}


void add(struct node **q,int num)
{
struct node *temp;
temp = *q;
if(*q==NULL)
{
*q=malloc(sizeof(struct node));
temp = *q;
}
else
{
while((temp->link)!=NULL)
{
temp=temp->link;
}
temp->link = malloc(sizeof(struct node));
temp=temp->link;
}
temp->data = num;
temp->link  = NULL;
}

void display(struct node *pt)
{

while(pt!=NULL)
{

printf("

 Data : %d",pt->data);
printf("
 Link : %d",pt->link);
pt=pt->link;
}
}


void invert(struct node *ptr)
{

struct node  *p,*q,*r;
p=ptr;
q=NULL;

while(p!=NULL)
{
r=q;
q=p;
p=p->link;
q->link=r;
}
ptr = q;
display(ptr);
}


// CONCATENATION OF LINKED LISTS

struct node * concat(struct node *p,struct node *q)
{
struct node *x,*r;


if (p==NULL)
r=q;

if (q==NULL)
r=p;
else
{
      x=p;
      r=x;
      while(x->link!=NULL)
x=x->link;
      x->link=q;
}
    return(r);
}


// SEARCHING AN ELEMENT IN THE LINKED LIST
// THIS FUNCTION FINDS THE FIRST OCCURENCE OF
// A DATA AND RETURNS A POINTER TO ITS ADDRESS

struct node * search(struct node *p)
{
struct node *temp;
int num;
temp = p;
printf("
 Enter the data that you want to search    ");
scanf("%d",&num);
printf("
 Link of temp %u", temp->link);
while(temp->link!=NULL)
{
printf("
 In while ");
if(temp->data == num)
return(temp);
temp=temp->link;
}
return(NULL);
}



// DELETING DATA FROM THE LINKED LIST//

void del(struct node *p,int num)
{

struct node *temp,*x;
temp=p;
x= NULL;

while (temp->link !=NULL)
{
if(temp->data == num)
{
if (x==NULL)
{
p = temp->link;
free(temp);
return;
}
else
{
x->link = temp->link;
free(temp);
return;
}
}                  //end of outer if
x=temp;
temp=temp->link;
} //end of while
printf("

No such entry to delete ");
} //end of fn.