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Program to implement Linear Queues using Linked list using global front and rear pointers

Program to implement Linear Queues using Linked list using global front and rear pointers

October 2, 2012 Comments Off on Program to implement Linear Queues using Linked list using global front and rear pointers By admin

Queues

Program to implement Linear Queues using Linked list using global front and rear pointers

/*Implementation of Linear Queues using Linked List
using global front and rear pointers*/

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>

typedef struct queue
{int info;
struct queue *next;
}queue;

queue *front=NULL,*rear=NULL;

queue *create()
{queue *temp=(queue *)malloc(sizeof(queue));
if(temp==NULL)
{printf(“Memory Allocation Error!”);
exit(1);
}
return temp;
}

queue *makenode(int x)
{queue *temp=create();
temp->info=x;
temp->next=NULL;
return temp;
}

/*Enqueue operation references rear pointer
to insert a new node at the next address of rear*/

void enqueue(int x)
{
queue *temp=makenode(x);
if(front==NULL)
{front=temp;
rear=temp;
}
else/*rear pointer referred without traversing entire queue*/
{rear->next=temp;
rear=temp;
}
}
void dequeue()
{
queue *temp=front;
if(front==NULL)
{printf(“nQueue Underflow!”);
exit(1);
}
front=front->next;
free(temp);
}

void display()
{queue *temp=front;
while(temp!=NULL)
{printf(“%d->”,temp->info);
temp=temp->next;
}
printf(“bb “);
}

void main()
{
int num,ch;
while(1)
{
clrscr();
printf(“nMenu”);
printf(“nn1. Enqueue”);
printf(“n2. Dequeue”);
printf(“n3. Display”);
printf(“n4. Exit”);
printf(“nnEnter your choice?”);
scanf(“%d”,&ch);
switch(ch)
{
case 1: printf(“nEnter an element?”);
scanf(“%d”,&num);
enqueue(num);
break;
case 2: printf(“Removing front element from the queue…!”);
dequeue();
break;
case 3: display();
break;
case 4: exit(0);
default:printf(“nInvalid choice…!”);
}
getch();
}
}

 

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