Queue implementation using Linked List

20. Program for implementing queue using linked list?

Program

#include<stdio.h>

#include<conio.h>

struct node            //declaring the structure of linked list

          {

          int data;

          struct node *link;

          }*front=NULL,*rear=NULL;

void ins()                         //Insert operation

          {

          struct node *temp;

          int item;

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

          printf("Enter the element to be inserted:\t");

          scanf("%d",&item);

          temp->data=item;

          temp->link=NULL;

          if(front==NULL)               //if list is empty

                   front=temp;

          else

                   rear->link=temp;

          rear=temp;

          }

void del()                                  //deletion operation

          {

          struct node *temp;

          if(front==NULL)                         //if list is empty

                   printf("\tQueue underflow\n");

          else

                   {

                   temp=front;

                   printf("The deleted element is %d\n",temp->data);

                   front=front->link;

                   free(temp);

                   }

          }

void display()

          {

          struct node *ptr;

          ptr=front;

          if(front==NULL)

                   printf("The stack is empty\n");

          else

                   {

                   printf("The Queue elements are:\n");

                   while(ptr!=NULL)

                             {

                             printf("%d\t",ptr->data);

                             ptr=ptr->link;

                             }

                   }

          }

void main()

          {

          int ch,i;

          char c;

          clrscr();

          do

          {

          printf("Enter the choice\t1.Insertion\t2.Deletion\t3.Display\n");

          scanf("%d",&ch);

          switch(ch)

                   {

                   case 1:

                             ins();           //calling insertion function

                             break;

                   case 2:

                             del();           //calling deletion function

                             break;

                   case 3:

                             display();               //calling display function

                             break;

                   default:

                             printf("\nWRONG CHOICE\n");

                             break;

                   }

                   printf("\nDo you want to continue:(y/n)?\n");

                   scanf(" %c",&c);

                   }

                   while((c=='y')||(c=='Y'));

          getch();

          }

Output

Enter the choice        1.Insertion     2.Deletion      3.Display

1

Enter the element to be inserted:       1

Do you want to continue:(y/n)?

y

Enter the choice        1.Insertion     2.Deletion      3.Display

1

Enter the element to be inserted:       2

Do you want to continue:(y/n)?

y

Enter the choice        1.Insertion     2.Deletion      3.Display

3

The Queue elements are:

1       2

Do you want to continue:(y/n)?

y

Enter the choice        1.Insertion     2.Deletion      3.Display

2                                                                

The deleted element is 1

Do you want to continue:(y/n)?

y

Enter the choice        1.Insertion     2.Deletion      3.Display

3

The Queue elements are:

2

Do you want to continue:(y/n)?

y

Enter the choice        1.Insertion     2.Deletion      3.Display

2

The deleted element is 2

Do you want to continue:(y/n)?

y

Enter the choice        1.Insertion     2.Deletion      3.Display

3                                         

The stack is empty

Do you want to continue:(y/n)?

y

Enter the choice        1.Insertion     2.Deletion      3.Display

2

          Queue underflow

Do you want to continue:(y/n)?

n