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queue.cpp
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queue.cpp
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#include<iostream>
using namespace std;
#define MAX_SIZE 101 //maximum size of the array that will store Queue.
// Creating a class named Queue.
class Queue
{
private:
int A[MAX_SIZE];
int front, rear;
public:
// Constructor - set front and rear as -1.
// We are assuming that for an empty Queue, both front and rear will be -1.
Queue()
{
front = -1;
rear = -1;
}
// To check wheter Queue is empty or not
bool IsEmpty()
{
return (front == -1 && rear == -1);
}
// To check whether Queue is full or not
bool IsFull()
{
return (rear+1)%MAX_SIZE == front ? true : false;
}
// Inserts an element in queue at rear end
void Enqueue(int x)
{
cout<<"Enqueuing "<<x<<" \n";
if(IsFull())
{
cout<<"Error: Queue is Full\n";
return;
}
if (IsEmpty())
{
front = rear = 0;
}
else
{
rear = (rear+1)%MAX_SIZE;
}
A[rear] = x;
}
// Removes an element in Queue from front end.
void Dequeue()
{
cout<<"Dequeuing \n";
if(IsEmpty())
{
cout<<"Error: Queue is Empty\n";
return;
}
else if(front == rear )
{
rear = front = -1;
}
else
{
front = (front+1)%MAX_SIZE;
}
}
// Returns element at front of queue.
int Front()
{
if(front == -1)
{
cout<<"Error: cannot return front from empty queue\n";
return -1;
}
return A[front];
}
/*
Printing the elements in queue from front to rear.
This function is only to test the code.
This is not a standard function for Queue implementation.
*/
void Print()
{
// Finding number of elements in queue
int count = (rear+MAX_SIZE-front)%MAX_SIZE + 1;
cout<<"Queue : ";
for(int i = 0; i <count; i++)
{
int index = (front+i) % MAX_SIZE; // Index of element while travesing circularly from front
cout<<A[index]<<" ";
}
cout<<"\n\n";
}
};
int main()
{
/*Driver Code to test the implementation
Printing the elements in Queue after each Enqueue or Dequeue
*/
Queue Q; // creating an instance of Queue.
Q.Enqueue(2); Q.Print();
Q.Enqueue(4); Q.Print();
Q.Enqueue(6); Q.Print();
Q.Dequeue(); Q.Print();
Q.Enqueue(8); Q.Print();
}