Implementation of Queues using Linked List in C

February 23, 2023

Implementation of Queues using Linked List in C

How to implement Queue using linked list?

Implementation of Queues using Linked List in C solves the problem of Queue implementation with arrays as using linked list for implementing queue we need not to define the size of the queue and it can work on the infinite number of values.

Implementing queue using linked list will not change its behavior i.e. the queue will continue to work with FIFO architecture.

Queue Using Linked List in C

enqueue(data)

  • Build a new node with given data.
  • Check if the queue is empty or not.
  • If queue is empty then assign new node to front and rear.
  • Else make next of rear as new node and rear as new node.

dequeue()

  • Check if queue is empty or not.
  • If queue is empty then dequeue is not possible.
  • Else store front in temp
  • And make next of front as front.

print()

  • Check if there is some data in the queue or not.
  • If the queue is empty print “No data in the queue.”
  • Else define a node pointer and initialize it with front.
  • Print data of node pointer until the next of node pointer becomes NULL.
Implementation of Queues using Linked List in C
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Queues In Data Structures

Implement Queue using Stack

Implement Queue using two Stacks

Circular queue in C

Circular queue using Array

Algorithm for enqueue(int d)

  • STRUCT NODE* NEW_N
  • NEW_N->DATA = D
  • NEW_N->NEXT = NULL
  • IF((FRONT == NULL)&&(REAR == NULL))
  • FRONT = REAR = NEW_N
  • ELSE
  • REAR->NEXT = NEW_N
  • REAR = NEW_N

Algorithm for dequeue()

  • STRUCT NODE *TEMP
  • TEMP = FRONT
  • IF((FRONT == NULL)&&(REAR == NULL))
  • RETURN
  • ELSE
  • FRONT = FRONT->NEXT
  • FREE(TEMP)

print()

  • STRUCT NODE* TEMP
  • IF((FRONT == NULL)&&(REAR == NULL))
  • RETURN
  • ELSE
  • TEMP = FRONT
  • WHILE(TEMP)
  • RETURN TEMP->DATA
  • TEMP = TEMP->NEXT

Code for implementing queue using linked list in C

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

struct node
{
	int data;
	struct node* next;
};//defining linked list to implement queue

struct node *front = NULL;
struct node *rear = NULL;

void enqueue(int d)//function to insert a node in queue
{
	struct node* new_n;
	new_n = (struct node*)malloc(sizeof(struct node));
	new_n->data = d;
	new_n->next = NULL;
	if((front == NULL)&&(rear == NULL)){
		front = rear = new_n;
	}
	else{
		rear->next = new_n;
		rear = new_n;
	}
	
}

void display()//function to display the queue
{
	struct node* temp;
	if((front == NULL)&&(rear == NULL)){
		printf("\nQueue is Empty");
	}
	else{
		temp = front;
		while(temp){
			printf(" %d ",temp->data);
			temp = temp->next;
		}
	}
}

void dequeue()//function to delete an element from a queue
{
	struct node *temp;
	temp = front;
	if((front == NULL)&&(rear == NULL)){
		printf("\nQueue is Empty");
	}
	else{
		front = front->next;
		free(temp);
	}
}
int main()//main function to use all our declared function
{
  enqueue(5);
  enqueue(10);
  enqueue(15);
  enqueue(20);
  enqueue(25);
  printf("Queue:");
  display();
  printf("\nQueue After Dequeue:");
  dequeue();
  display();
  
}

Output

Queue: 5  10  15  20  25 
Queue After Dequeue: 10  15  20  25

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Stacks

Queues

Circular Queues

Priority Queue

  • Application of Priority Queue
  • Priority Queue Example
  • Priority Queue Introduction – C | C++ | Java
  • Priority Queue Implementation using Array – C | C++ | Java
  • Priority Queue using Linked List – C | C++ | Java
  • Priority Queue Insertion and Deletion- C | C++ | Java

Stacks

  • Introduction to Stack in Data Structure
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  • Stack: Infix, Prefix and Postfix conversions
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  • Representation of a Stack as an Array. –
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  • Implementation of Queues using Arrays | C Program
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  • Types of Queues in Data Structure
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  • Reverse a Queue –
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  • Queues using Linked Lists –
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  • Implement Queue using Stack –
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  • Implement Queue using two Stacks –
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Circular Queues

Priority Queue

  • Application of Priority Queue
  • Priority Queue Example
  • Priority Queue Introduction –
    C | C++ | Java
  • Priority Queue Implementation using Array –
    C | C++ | Java
  • Priority Queue using Linked List –
    C | C++ | Java
  • Priority Queue Insertion and Deletion-
    C | C++ | Java