Write a C program to implement queue operations using linked list

By | April 10, 2017

Implement queue operations using linked list 


Write a C program to implement queue operations using linked list. Here’s simple program to implement queue operations using linked list in C Programming Language.


What is Queue ?


Queue is also an abstract data type or a linear data structure, in which the first element is inserted from one end called REAR, and the deletion of existing element takes place from the other end called as FRONT.

This makes queue as FIFO data structure, which means that element inserted first will also be removed first.


Basic Operations : :


  • enqueue() − add (store) an item to the queue.
  • dequeue() − remove (access) an item from the queue.
  • peek() − Gets the element at the front of the queue without removing it.
  • isfull() − Checks if the queue is full.
  • isempty() − Checks if the queue is empty.

Below is the source code for C program to implement queue operations using linked list which is successfully compiled and run on Windows System to produce desired output as shown below :


SOURCE CODE : :


/* C program to implement queue operations using linked list */


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

struct node
{
	int info;
	struct node *link;
}*front=NULL,*rear=NULL;

void insert(int item);
int del();
int peek();
int isEmpty();
void display();

int main()
{
	int choice,item;
	while(1)
	{
		printf("\n1.Insert\n");
		printf("2.Delete\n");
		printf("3.Display the element at the front\n");
		printf("4.Display all elements of the queue\n");
		printf("5.Quit\n");
		printf("\nEnter your choice : ");
		scanf("%d", &choice);

		switch(choice)
		{
		case 1:
			printf("\nInput the element for adding in queue : ");
			scanf("%d",&item);
			insert(item);
			break;
		case 2:
			printf("\nDeleted element is  %d\n",del());
			break;
		case 3:
			printf("\nElement at the front of the queue is %d\n", peek() );
			break;
		case 4:
			display();
			break;
		case 5:
			exit(1);
		default :
			printf("\nWrong choice\n");
		}/*End of switch*/
	}/*End of while*/
}/*End of main()*/

void insert(int item)
{
	struct node *tmp;
	tmp=(struct node *)malloc(sizeof(struct node));
	if(tmp==NULL)
	{
		printf("\nMemory not available\n");
		return;
	}
	tmp->info = item;
	tmp->link=NULL;
	if(front==NULL)		 /*If Queue is empty*/
		front=tmp;
	else
		rear->link=tmp;
	rear=tmp;
}/*End of insert()*/

int del()
{
	struct node *tmp;
	int item;
	if( isEmpty( ) )
	{
		printf("\nQueue Underflow\n");
		exit(1);
	}
	tmp=front;
	item=tmp->info;
	front=front->link;
	free(tmp);
	return item;
}/*End of del()*/

int peek()
{
	if( isEmpty( ) )
	{
		printf("\nQueue Underflow\n");
		exit(1);
	}
	return front->info;
}/*End of peek()*/

int isEmpty()
{
	if(front==NULL)
		return 1;
	else
		return 0;

}/*End of isEmpty()*/

void display()
{
	struct node *ptr;
	ptr=front;
	if(isEmpty())
	{
		printf("\nQueue is empty\n");
		return;
	}
	printf("\nQueue elements :\n\n");
	while(ptr!=NULL)
	{
		printf("%d ",ptr->info);
		ptr=ptr->link;
	}
	printf("\n\n");
}/*End of display()*/

OUTPUT : :

/* C program to implement queue operations using linked list */

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 1

Input the element for adding in queue : 1

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 1

Input the element for adding in queue : 2

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 1

Input the element for adding in queue : 3

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 1

Input the element for adding in queue : 4

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 4

Queue elements :

1 2 3 4


1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 2

Deleted element is  1

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 2

Deleted element is  2

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 3

Element at the front of the queue is 3

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 4

Queue elements :

3 4


1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 2

Deleted element is  3

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 2

Deleted element is  4

1.Insert
2.Delete
3.Display the element at the front
4.Display all elements of the queue
5.Quit

Enter your choice : 2

Queue Underflow

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