Question

(C++) (VISUAL STUDIO)

Circular Queue is a linear data structure in which the operations are performed based on FIFO (First In First Out) principle and the last position is connected back to the first position to make a circle. In a normal Queue, we can insert elements until queue becomes full. But once queue becomes full, we cannot insert the next element even if there is a space in front of queue.

Efficiently implement a queue class using a circular array. You may use a vector

(rather than a primitive array) as the underlying array structure.

template <typename Object>

class Queue {

private:

       vector<Object> que;

       int front, rear,capacity,size;

public:

       Queue(int maxsize);

       void enqueue(const Object & x);

       const Object& dequeue();

       bool empty() const;

       bool full() const;;

};

Write an appropriate main to test the functionality of queue class.

Answer 1

Solution:

#include<iostream>

#include<vector>

using namespace std;

template <typename T>

class Queue

{

private:

vector<T> que;

int front, rear, capacity, size;

public:

//Constructor

Queue(int maxSize)

{

this->front = this->rear = -1;

this->size = maxSize;

this->que.resize(maxSize);

}

//enqueue function

void enqueue(const T x)

{

if (this->full())

{

cout << "queue is full";

}

else

{

this->rear = (this->rear + 1) % this->size;

this->que[this->rear] = x;

if (this->front == -1)

this->front = this->rear;

}

}

//dequeue function

const T dequeue()

{

if (this->empty())

{

cout << "Queue is Empty";

return 0;

}

else

{

T& data = this->que[this->front];

if (this->front == this->rear)

this->front = this->rear = -1;

else

this->front = (this->front + 1) % this->size;

return data;

}

}

bool empty()

{

return (this->front == -1);

}

bool full()

{

return ((this->rear + 1) % this->size == this->front);

}

void display()

{

int front_pos = this->front, rear_pos = this->rear;

if (front == -1)

{

cout << "Queue is empty\n";

return;

}

cout << "Queue elements :\n";

if (front_pos <= rear_pos)

{

while (front_pos <= rear_pos)

{

cout << this->que[front_pos] << " ";

front_pos++;

}

}

else

{

while (front_pos <= this->size - 1)

{

cout << this->que[front_pos] << " ";

front_pos++;

}

front_pos = 0;

while (front_pos <= rear_pos)

{

cout << this->que[front_pos] << " ";

front_pos++;

}

}

cout << "\n";

cout << endl;

}

};

//main function to test code

int main()

{

int choice, item;

Queue<int> q(10);

do

{

cout << "1.Enqueue\n";

cout << "2.Dequeue\n";

cout << "3.Display\n";

cout << "4.Quit\n";

cout << "Enter your choice : ";

cin >> choice;

switch (choice)

{

case 1:

cout << "Enter the element to insert in the queue : ";

cin >> item;

q.enqueue(item);

break;

case 2:

q.dequeue();

break;

case 3:

q.display();

break;

case 4:

break;

default:

cout << "Wrong choice\n";

}/*End of switch*/

} while (choice != 4);

return 0;

}

Output: