Queue implemented with SLL Code FIFO Queue using single liked list to hold a lis

Question

Queue implemented with SLL

Code FIFO Queue using single liked list to hold a list of integers. Use the C++ “struct” structure to create your queue items.

The user should be able to enter the values, once entered should be able to perform all the functions listed below

InitQueue – Initialize FIFO Queue

IsEmptyQueue – Checks for empty Queue

FrontQueue – Returns from item

BackQueue – Returns back item

PushQueue – Adds an item to end of Queue

PopQueue – Delete an item from of Queue

ClearQueue – Delete all items on the Queue

PrintQueue - Display all elements on the Queue

Explanation / Answer

Answer:

#include<iostream>
#include<cstdlib>
using namespace std;
struct node
{
   int data;
   struct node *next;
}*p=NULL,*q=NULL,*front=NULL,*rear=NULL;
void InitQueue()
{
   front=rear=NULL;
   cout<<"Queue is Initialized ";
}
int IsEmptyQueue()
{
   if(front==NULL)
   return 0;
   else
   return 1;
}
int FrontQueue()
{
   q=front;
   if(q!=NULL)
   {
       cout<<"The First Element is:"<<q->data<<endl;
   }
   else
   cout<<"Queue is empty ";
}
int BackQueue()
{
   q=front;
   if(q==NULL)
cout<<"Queue is Empty ";
   else
   {
   while(q->next!=NULL)
   {
       q=q->next;
   }
   cout<<"The Last Element is "<<q->data<<endl;
}
}
void PushQueue(int x)
{
   p=new node;
   p->data=x;
   p->next=NULL;
   if(front==NULL)
   {
       front=rear=p;
       rear->next=NULL;
   }
   else
   {
       rear->next=p;
       rear=p;
       rear->next=NULL;
   }  
}
int PopQueue()
{
   int x;
   if(front==NULL)
   cout<<"Queue is empty ";
   else
   {
       q=front;
       x=q->data;
       front=front->next;
       delete(q);
       return x;
   }
}
void ClearQueue()
{
   node *temp;
   while(front!=NULL)
   {
       temp=front;
       front=front->next;
       free(temp);
   }
   front=rear=NULL;
}
void PrintQueue()
{
   p=front;
   if(front==NULL)
   cout<<"No items to display ";
   else
   {
       cout<<"The Queue elements are ";
       while(p!=NULL)
       {
           cout<<p->data<<" ";
           p=p->next;
       }
       cout<<endl;
   }
}
int main()
{
   int choice,value,i;
   cout<<"Displaying Menu ";
   cout<<"1.Initialize Queue ";
   cout<<"2.Check Queue empty ";
   cout<<"3.Display First item ";
   cout<<"4.Display Last item ";
   cout<<"5.Push an item ";
   cout<<"6.Pop an item ";
   cout<<"7.Clear the Queue ";
   cout<<"8.Print Queue elements ";
   cout<<"0.exit ";
   while(1)
   {
   cout<<"Enter your choice (1-8) and 0 to exit:";
   cin>>choice;
   switch(choice)
   {
       case 1:InitQueue();
       break;
       case 2:i=IsEmptyQueue();
       if(i==0)
       cout<<"Queue is Empty ";
       else
       cout<<"Queue is not Empty ";
       break;
       case 3:FrontQueue();
       break;
       case 4:BackQueue();
       break;
       case 5:cout<<"Enter an element to be pushed:";
       cin>>value;
       PushQueue(value);
       break;
       case 6:value=PopQueue();
       cout<<"The deleted element is:"<<value<<endl;
       break;
       case 7:cout<<"Clearing Queue items.."<<endl;
       ClearQueue();
       break;
       case 8:PrintQueue();
       break;
       case 0:exit(0);
       default:cout<<"Invalid Choice";     
}
   }
return 0;
}

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