queueLL.cpp

#include <iostream>
using namespace std;

struct QueueNode
{
    int data;
    QueueNode* next;
} *front = NULL, *rear = NULL;

void Enqueue(int value){
    QueueNode* newNode = (QueueNode*)malloc(sizeof(QueueNode));
    newNode->data = value;
    newNode->next = NULL;

    if (front == NULL)
    {
        front = newNode;
        rear = newNode;
    }
    else{
        rear->next = newNode;
        rear = rear->next;
    }
}
void DeQueue(){
    if (front == NULL)
    {
        cout<<"Queue is empty"<<endl;
        return;
    }
    QueueNode* temp = front;
    front = front->next;
    free(temp);
}
void display(){
    if (front == NULL)
    {
        cout<<"Queue is empty"<<endl;
        return;
    }
    QueueNode* curr = front;
    while (curr != NULL)
    {
        cout<<curr->data<<"->";
        curr = curr->next;
    }
    cout<<"NULL\n";
}
int main(int argc, char const *argv[])
{
    int choice,value;
    while(true){
        cout<<"1: EnQueue"<<endl;
        cout<<"2: DeQueue"<<endl;
        cout<<"3: View Elements"<<endl;
        cout<<"4: Exit"<<endl;
        cout<<"Enter which operation would you like to perform : "<<endl;
        cin>>choice;
        switch (choice)
        {
        case 1:
            cout<<"Enter value to be inserted:";
            cin>>value;
            Enqueue(value);
            break;
        case 2:
            DeQueue();
            break;
        case 3:
            display();
            break;
        case 4:
            cout<<"Exiting...\n";
            break;
        default:
            break;
        }
        if (choice >= 4)
        {
            break;
        }
    }
    return 0;
}