Question

PROBLEM:

string CBQueue::dequeue( )

This method should remove and return the item at the front of the queue- please add comments

EXISTING CODE:

#include // this allows you to declare and use strings

#include

using namespace std;

struct qNode

{

  string data;

  qNode* next;

  qNode* prev;

};

class CBQueue

{

  public:

    CBQueue();

int CBQueue::getSize( );

bool CBQueue::isEmpty( );

  private:

    qNode* front;

    qNode* rear;

    int size;

};

#include "CBQueue.h"

CBQueue::CBQueue()

{

front = NULL;

rear = NULL;

size = 0;

}

//Returns elements in CBQuene

int CBQueue::getSize( ){

return size;

}

//return whether the queue is empty or not

bool CBQueue::isEmpty( ){

if(front == NULL)}{

return true;

}

else{

return false;

}

//

void CBQueue::enqueue(string s){

//Create a structure of Node which will hold the data s

struct qNode * temp = (struct qNode *)malloc(sizeof(struct qNode));

//data assigned as s

temp->data = s;

//initially prevIOUS pointer is NULL

temp->prev = NULL;

//initially next pointer is NULL

temp->next = NULL;

//If it is the first NODE

if (front == NULL)

{

//THEN FRONT AS REAR IS ASSIGNED AS TEMP

front = rear = temp;

}

else

{

//Otherwise add the new node to the rear end

rear->next = temp;

//Make temp previous as rear

temp->prev = rear;

//Now the temp becomes the rear

rear = temp;

}

//

void CBQuelue::printF2B( ){

temp = front;

//check if quene is empty

if ((front == NULL) && (rear == NULL)) {

cout<<"Queue is empty."<

return;

}

//if not empty-then print the items of the quene starting at the front and proceed to the rear

cout<<"Queue elements are (Front to Rear): ";

while (temp != NULL) { //while(temp)?

cout

temp = temp->next;

}

cout<

}

string CBQueue::dequeue( ){

}

Answer 1

string CBQueue::dequeue( ){

    // if the queue is empty

    if( this->front == NULL )

        return "";

    // if the queue is not empty

   else

    {

        // store the front element in the beginning of the queue

        string x = this->front->data;

       

        // make second node as the new front node

        this->front = this->front->next;

       

        // delete the previous front node

        delete this->front->prev;

        this->front->prev = NULL;

       

        return x;

    }

}