C Source Codes for Implementing Linked List

The linked list can be implemented using the pointer structure in C so that we can

• add an element
• delete an element
• search for an element
• concatenate two linked list
• Invert a linked list
• Display elements in the list

//Program to demonstrate linked list operations

# include<stdio.h>
# include<conio.h>
# 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
////();
will=1;
printf("Main Menu\n1. Add element\n2.Delete element\n3.Search element\n4Linked List concatenation\n5.Invert linked list\n6. Display elements\n7.To exit\n\nPlease enter the choice");
while(will==1)
{

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 \n\t");
    temp = search(ptr);
    printf("Address of first occurence is  %u \t",temp);
    break;
case 4:
    /* Inputs given internally for demo only */
    printf(" Now demonstrating linked list concatenation\tPress 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);
    //();
    printf("Now Displaying the result of concatenation");
    display(result);
    getch();
    break;
case 5:

    printf("Inverting the list ...Press any key to continue...\n\t");
    invert(ptr);
    break;
case 6:
    display(ptr);
    break;
case 7:
     exit(1);
     break;
default:
    printf("Illegal choice");
}
printf("DO you want to continue ?   ");
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("\tData : %d\t",pt->data);
    printf("Link : %d\t",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("\nIn while\n ");
    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("\n No such entry to delete \n");
}    //end of fn.