Question

Help me solve this in C++

Rewrite the code to use array instead of linked lists. Please do not change anything besides the data structure. Instead of linked list use an array. The functionality should remain exactly the same. You can prepare a class if you wish but it is not required.

/**
* Queue implementation using linked list C style implementation ( no OOP).
*/

#include <cstdio>
#include <cstdlib>
#include <climits>
#include <iostream>

#define CAPACITY 100 // Queue max capacity

using namespace std;
/** Queue structure definition */
struct QueueType
{
int data;
struct QueueType * next;
};
/** Queue size */
unsigned int size = 0;

int enqueue(QueueType * &rear, QueueType * &front, int data);
int dequeue(QueueType * &front);
int getRear(QueueType * &rear);
int getFront(QueueType * &front);
void display(QueueType * front);
int isEmpty();
int isFull();
string prepMenu();

int main()
{
int option, data;

QueueType *rear, *front;

rear = NULL;
front = NULL;
string menu = prepMenu();
cout << menu << endl;
cin >> option;
while (option !=7)
{

switch (option)
{
case 1:
cout << "\nEnter data to enqueue (-99 to stop): ";
cin >> data;
while ( data != -99)
{
/// Enqueue function returns 1 on success
/// otherwise 0
if (enqueue(rear, front, data))
cout << "Element added to queue.";
else
cout << "Queue is full." << endl;
cout << "\nEnter data to enqueue (-99 to stop): ";
cin >> data;
}

break;

case 2:
data = dequeue(front);

/// on success dequeue returns element removed
/// otherwise returns INT_MIN
if (data == INT_MIN)
cout << "Queue is empty."<< endl;
else
cout << "Data => " << data << endl;

break;

case 3:

/// isEmpty() function returns 1 if queue is emtpy
/// otherwise returns 0
if (isEmpty())
cout << "Queue is empty."<< endl;
else
cout << "Queue size => "<< size << endl;

break;

case 4:
data = getRear(rear);

if (data == INT_MIN)
cout << "Queue is empty." << endl;
else
cout << "Rear => " << data << endl;

break;

case 5:

data = getFront(front);

if (data == INT_MIN)
cout <<"Queue is empty."<< endl;
else
cout <<"Front => " << data << endl;

break;

case 6:
display(front);
break;

default:
cout <<"Invalid choice, please input number between (0-5).\n";
break;
}

cout <<"\n\n";
cout << menu<< endl;
cin >> option;
}
}

/**
* Enqueues/Insert an element at the rear of a queue.
* Function returns 1 on success otherwise returns 0.
*/
int enqueue(QueueType * &rear, QueueType * &front, int data)
{
QueueType * newNode = NULL;

/// Check queue out of capacity error
if (isFull())
{
return 0;
}

/// Create a new node of queue type
newNode = new QueueType;

/// Assign data to new node
newNode->data = data;

/// Initially new node does not point anything
newNode->next = NULL;

/// Link new node with existing last node
if ( (rear) )
{
rear->next = newNode;
}

/// Make sure newly created node is at rear
rear = newNode;

/// Link first node to front if its NULL
if ( !( front) )
{
front = rear;
}

/// Increment quque size
size++;

return 1;
}

/**
* Dequeues/Removes an element from front of the queue.
* It returns the element on success otherwise returns
* INT_MIN as error code.
*/
int dequeue(QueueType * &front)
{
QueueType *toDequque = NULL;
int data = INT_MIN;

// Queue empty error
if (isEmpty())
{
return INT_MIN;
}

/// Get element and data to dequeue
toDequque = front;
data = toDequque->data;

/// Move front ahead
front = (front)->next;

/// Decrement size
size--;

/// Clear dequeued element from memory
free(toDequque);

return data;
}

/**
* Gets, element at rear of the queue. It returns the element
* at rear of the queue on success otherwise return INT_MIN as
* error code.
*/
int getRear(QueueType * & rear)
{
// Return INT_MIN if queue is empty otherwise rear.
return (isEmpty())
? INT_MIN
: rear->data;
}

/**
* Gets, element at front of the queue. It returns the element
* at front of the queue on success otherwise return INT_MIN as
* error code.
*/
int getFront(QueueType * &front)
{
// Return INT_MIN if queue is empty otherwise front.
return (isEmpty())
? INT_MIN
: front->data;
}

/**
* Checks, if queue is empty or not.
*/
int isEmpty()
{
return (size <= 0);
}

/**
* Checks, if queue is within the maximum queue capacity.
*/
int isFull()
{
return (size > CAPACITY);
}
string prepMenu()
{

string menu = "";

menu+= " \n-------------------------------------------------------------------\n";
menu+= "1.Enqueue 2.Dequeue 3.Size 4.Get Rear 5.Get Front 6.Display 7.Exit\n";
menu+= "----------------------------------------------------------------------\n";
menu+= "Select an option: ";
return menu;
}
void display(QueueType * front)
{
for ( QueueType *t = front; t !=NULL; t = t->next)
cout <<t->data << " ";
cout << endl << endl;
}

Answer 1

#include <cstdio>
#include <cstdlib>
#include <climits>
#include <iostream>

#define CAPACITY 100 // Queue max capacity

using namespace std;
/** Queue structure definition */

unsigned int size = 0;
struct Queue {
int front, rear, capacity;
int* queue;
Queue(int c)
{

front = rear = 0;
capacity = c;
queue = new int;
}

~Queue() { delete[] queue; }

// function to insert an element
// at the rear of the queue
void queueEnqueue(int data)
{
// check queue is full or not
if (capacity == rear) {
cout<<"Queue is full"<<endl;
return;
}

// insert element at the rear
else {
queue[rear] = data;
rear++;
}
return;
}

// function to delete an element
// from the front of the queue
void queueDequeue()
{
// if queue is empty
if (front == rear) {
cout<<"\nQueue is empty\n";
return;
}

// shift all the elements from index 2 till rear
// to the left by one
else {
for (int i = 0; i < rear - 1; i++) {
queue[i] = queue[i + 1];
}

// decrement rear
rear--;
}
return;
}

// print queue elements
void queueDisplay()
{
int i;
if (front == rear) {
cout<<"\nQueue is Empty\n";
return;
}

// traverse front to rear and print elements
for (i = front; i < rear; i++) {
cout<<" <-- " << queue[i];
}
return;
}

// print front of queue
void queueFront()
{
if (front == rear) {
cout<<"\nQueue is Empty\n";
return;
}
cout<<"\nFront Element is: %d" << queue[front];
return;
}

void queuerear()
{
if (front == rear) {
printf("\nQueue is Empty\n");
return;
}
printf("\nFront Element is: %d", queue[rear]);
return;
}
int getsize()
{
if (front == rear)
cout << "Queue is empty."<< endl;
else
cout << "Queue size => "<< capacity << endl;

}
};

string prepMenu();

int main()
{
int option, data;
Queue obj(100);

string menu = prepMenu();
cout << menu << endl;
cin >> option;
while (option !=7)
{

switch (option)
{
case 1:
cout << "\nEnter data to enqueue (-99 to stop): ";
cin >> data;

obj.queueEnqueue(data);

break;

case 2:
obj.queueDequeue();
break;

case 3:

obj.getsize();

break;

case 4:
obj.queuerear();

break;

case 5:

obj.queueFront();
break;

case 6:
obj.queueDisplay();
break;

default:
cout <<"Invalid choice, please input number between (0-5).\n";
break;
}

cout <<"\n\n";
cout << menu<< endl;
cin >> option;
}
}

string prepMenu()
{

string menu = "";

menu+= " \n-------------------------------------------------------------------\n";
menu+= "1.Enqueue 2.Dequeue 3.Size 4.Get Rear 5.Get Front 6.Display 7.Exit\n";
menu+= "----------------------------------------------------------------------\n";
menu+= "Select an option: ";
return menu;
}

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