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Linked List Implementation of a Queue

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Said HR answered on April 10, 2022 Popularity 10/10 Helpfulness 1/10

answer Linked List Implementation of a Queue

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Linked List Implementation of a Queue

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// A C program to demonstrate linked list based implementation of queue
#include <stdio.h>
#include <stdlib.h>
  
// A linked list (LL) node to store a queue entry
struct QNode {
    int key;
    struct QNode* next;
};
  
// The queue, front stores the front node of LL and rear stores the
// last node of LL
struct Queue {
    struct QNode *front, *rear;
};
  
// A utility function to create a new linked list node.
struct QNode* newNode(int k)
{
    struct QNode* temp = (struct QNode*)malloc(sizeof(struct QNode));
    temp->key = k;
    temp->next = NULL;
    return temp;
}
  
// A utility function to create an empty queue
struct Queue* createQueue()
{
    struct Queue* q = (struct Queue*)malloc(sizeof(struct Queue));
    q->front = q->rear = NULL;
    return q;
}
  
// The function to add a key k to q
void enQueue(struct Queue* q, int k)
{
    // Create a new LL node
    struct QNode* temp = newNode(k);
  
    // If queue is empty, then new node is front and rear both
    if (q->rear == NULL) {
        q->front = q->rear = temp;
        return;
    }
  
    // Add the new node at the end of queue and change rear
    q->rear->next = temp;
    q->rear = temp;
}
  
// Function to remove a key from given queue q
void deQueue(struct Queue* q)
{
    // If queue is empty, return NULL.
    if (q->front == NULL)
        return;
  
    // Store previous front and move front one node ahead
    struct QNode* temp = q->front;
  
    q->front = q->front->next;
  
    // If front becomes NULL, then change rear also as NULL
    if (q->front == NULL)
        q->rear = NULL;
  
    free(temp);
}
  
// Driver Program to test above functions
int main()
{
    struct Queue* q = createQueue();
    enQueue(q, 10);
    enQueue(q, 20);
    deQueue(q);
    deQueue(q);
    enQueue(q, 30);
    enQueue(q, 40);
    enQueue(q, 50);
    deQueue(q);
    printf("Queue Front : %d \n", q->front->key);
    printf("Queue Rear : %d", q->rear->key);
    return 0;
}

Popularity 10/10 Helpfulness 1/10 Language whatever

Source: www.geeksforgeeks.org

Tags: implementation linked-list queue whatever

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Contributed on Aug 28 2022

Said HR

0 Answers Avg Quality 2/10

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implementation of queue using linked list in c

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

// Structure to create a node with data and next pointer
struct node {
	int data;
	struct node *next;
};

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

// Enqueue() operation on a queue
void enqueue(int value) {
	struct node *ptr;
	ptr = (struct node *)malloc(sizeof(struct node));
	ptr->data = value;
	ptr->next = NULL;
	if ((front == NULL) && (rear == NULL)) {
		front = rear = ptr;
	} else {
		rear->next = ptr;
		rear = ptr;
	}
	printf("Node is Inserted\n\n");
}

// Dequeue() operation on a queue
int dequeue() {
	if (front == NULL) {
		printf("\nUnderflow\n");
		return -1;
	} else {
		struct node *temp = front;
		int temp_data = front->data;
		front = front->next;
		free(temp);
		return temp_data;
	}
}

// Display all elements of queue
void display() {
	struct node *temp;
	if ((front == NULL) && (rear == NULL)) {
		printf("\nQueue is Empty\n");
	} else {
		printf("The queue is \n");
		temp = front;
		while (temp) {
			printf("%d--->", temp->data);
			temp = temp->next;
		}
		printf("NULL\n\n");
	}
}

int main() {
	int choice, value;
	printf("\nImplementation of Queue using Linked List\n");
	while (choice != 4) {
		printf("1.Enqueue\n2.Dequeue\n3.Display\n4.Exit\n");
		printf("\nEnter your choice : ");
		scanf("%d", &choice);
		switch (choice) {
		case 1:
			printf("\nEnter the value to insert: ");
			scanf("%d", &value);
			enqueue(value);
			break;
		case 2:
			printf("Popped element is :%d\n", dequeue());
			break;
		case 3:
			display();
			break;
		case 4:
			exit(0);
			break;
		default:
			printf("\nWrong Choice\n");
		}
	}
	return 0;
}

Popularity 10/10 Helpfulness 4/10 Language c

Source: www.scaler.com

Tags: c

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Contributed on Sep 20 2022

Digvijay Sunil

0 Answers Avg Quality 2/10

Java Queue Linked List Implementation

Comment

-1

class LinkedListQueue
{
 private Node front, rear; 
 private int queueSize; // queue size 
  
 //linked list node
 private class Node { 
 int data;
 Node next;
 }
  
 //default constructor - initially front & rear are null; size=0; queue is empty
 public LinkedListQueue()
 {
 front = null;
 rear = null;
 queueSize = 0;
 }
 
 
//check if the queue is empty
 public boolean isEmpty()
 {
 return (queueSize == 0);
 }
  
 //Remove item from the front of the queue.
 public int dequeue()
 {
 int data = front.data;
 front = front.next;
 if (isEmpty()) 
 {
 rear = null;
 }
 queueSize--;
 System.out.println("Element " + data+ " removed from the queue");
 return data;
 }
  
 //Add data at the rear of the queue.
 public void enqueue(int data)
 {
 Node oldRear = rear;
 rear = new Node();
 rear.data = data;
 rear.next = null;
 if (isEmpty()) 
 {
 front = rear;
 }
 else  {
 oldRear.next = rear;
 }
 queueSize++;
 System.out.println("Element " + data+ " added to the queue");
 }
 //print front and rear of the queue
 public void print_frontRear() {
     System.out.println("Front of the queue:" + front.data 
     + " Rear of the queue:" + rear.data);
 }
}
class Main{
 public static void main(String a[]){
  
 LinkedListQueue queue = new LinkedListQueue();
 
 queue.enqueue(6);
 queue.enqueue(3);
 queue.print_frontRear();
 queue.enqueue(12);
 queue.enqueue(24);
 queue.dequeue();
 queue.dequeue();
 queue.enqueue(9);
 
 queue.print_frontRear();
 }
}

Popularity 10/10 Helpfulness 3/10 Language java

Source: www.softwaretestinghelp.com

Tags: implementation impl

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Contributed on Apr 10 2022

Fo Angel

0 Answers Avg Quality 2/10

implementation of queue using linked list in c

Comment

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

// Structure to create a node with data and next pointer
struct node {
	int data;
	struct node *next;
};

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

// Enqueue() operation on a queue
void enqueue(int value) {
	struct node *ptr;
	ptr = (struct node *)malloc(sizeof(struct node));
	ptr->data = value;
	ptr->next = NULL;
	if ((front == NULL) && (rear == NULL)) {
		front = rear = ptr;
	} else {
		rear->next = ptr;
		rear = ptr;
	}
	printf("Node is Inserted\n\n");
}

// Dequeue() operation on a queue
int dequeue() {
	if (front == NULL) {
		printf("\nUnderflow\n");
		return -1;
	} else {
		struct node *temp = front;
		int temp_data = front->data;
		front = front->next;
		free(temp);
		return temp_data;
	}
}

// Display all elements of queue
void display() {
	struct node *temp;
	if ((front == NULL) && (rear == NULL)) {
		printf("\nQueue is Empty\n");
	} else {
		printf("The queue is \n");
		temp = front;
		while (temp) {
			printf("%d--->", temp->data);
			temp = temp->next;
		}
		printf("NULL\n\n");
	}
}

int main() {
	int choice, value;
	printf("\nImplementation of Queue using Linked List\n");
	while (choice != 4) {
		printf("1.Enqueue\n2.Dequeue\n3.Display\n4.Exit\n");
		printf("\nEnter your choice : ");
		scanf("%d", &choice);
		switch (choice) {
		case 1:
			printf("\nEnter the value to insert: ");
			scanf("%d", &value);
			enqueue(value);
			break;
		case 2:
			printf("Popped element is :%d\n", dequeue());
			break;
		case 3:
			display();
			break;
		case 4:
			exit(0);
			break;
		default:
			printf("\nWrong Choice\n");
		}
	}
	return 0;
}

Popularity 9/10 Helpfulness 3/10 Language c

Source: www.scaler.com

Tags: c implementation implementat

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Contributed on Sep 20 2022

Digvijay Sunil

0 Answers Avg Quality 2/10

Queue using linked list

Comment

#include<iostream>
using namespace std;

class node{
	public:
		int data;
		node *next;
		void EnQueue();
		void DeQueue();
		void display();
};
node *rear=NULL;
void node::EnQueue()
{
	
		
	if(rear==NULL)
	{
		rear=new node();
			cout<<"Enter data : ";
			cin>>rear->data;
	}
	else
	{
	static node *temp=rear;
	node *newnode;
	newnode=new node();
	cout<<"Enter data : ";
	cin>>newnode->data;
	newnode->next=NULL;
	temp->next=newnode;
	temp=temp->next;
	}
}

void node::DeQueue()
{
	if(rear==NULL)
	{
		cout<<"The Queue is Underflow!";
	}
	else
	{
	cout<<"Dequeued element is : "<<rear->data;
	rear=rear->next;
	}
}

void node::display()
{
	node* temp=rear;
	if(rear==NULL)
	{
		cout<<"\nThe Queue is Empty!\n";
	}
	else
	{
		while(temp!=NULL)
		{
		cout<<temp->data<<" ";
		temp=temp->next;
		}
	}
}
int main()
{
	node obj;
 int ch;
   
    while(ch!=4){
    	cout<<"\n1) Push in stack"<<endl;
   		cout<<"2) Pop from stack"<<endl;
   		cout<<"3) Display stack"<<endl;
  		cout<<"4) Exit"<<endl;
    	cout<<"Enter choice: "<<endl;
      cin>>ch;
      switch(ch) {
         case 1: {
            obj.EnQueue();
            break;
         }
         case 2: {
            obj.DeQueue();
            break;
         }
         case 3: {
            obj.display();
            break;
         }
         case 4: {
            exit(0);
            break;
         }
         default: {
            cout<<"Invalid Choice"<<endl;
         }
	
}
}
}

Popularity 9/10 Helpfulness 2/10 Language cpp

Source: Grepper

Tags: c++ linked-list link

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Contributed on Sep 06 2023

talha shahid

0 Answers Avg Quality 2/10

Linked List Implementation of a Queue

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