Question

lab 11

Do not change main.cpp, i need c++ code for queue.h and queue.cpp

Given the complete main() function, partial queue class header queue.h, and queue.cpp, you will complete the class declaration and class implementation. The following member functions are required:

• constructor
• enqueue()
• dequeue()

You may elect to create the following helper functions:

• isFull()
• isEmpty()

A description of these ADT operations are available in this Zybook and in the textbook's chapter 17.

Example: If the input is:

3
Led Zepplin
Linda Ronstadt
Elton John

where 3 is the number of phrases, and each subsequent phrase, the output is:

Led Zepplin Linda Ronstadt Elton John

The queue is a fixed size and is implemented as an array. You may NOT use any STL features.

main.cpp:

#include <iostream>
#include "queue.h"
using namespace std;

int main()
{
queue q;
string item;
int num = 0;

cin >> num >> ws;
for (int i=0; i<num; i++)
{
   getline(cin, item);
   q.enqueue(item);
}

for (int i=0; i<num; i++)
   cout << q.dequeue() << " ";

cout << endl;

return 0;
}

queue.h

#ifndef QUEUE_H
#define QUEUE_H

#include <string>

/*
* QUEUESIZE should be one more than the desired queue size
* The queue will hold QUEUESIZE-1 elements
* The unused element is used to distinguish full versus empty
*/
const int QUEUESIZE = 11;

class queue
{
public:

// TODO: implement the public members as described in the specification

private:

// TODO: implement the private member as described in the specification

};

#endif

queue.cpp

#include "queue.h"

// TODO: implement the class member functions

Answer 1

Summary :

Provided the solution with following (i) Details of appraoch (ii) Code for queue.h & queue.cpp & (iii) Sample Output

Appraoch :

Implemented the queue using teh array of strings ( this can be easily templatized as well by replacing string with a template declaration ).

The private memebers list holds the queue members , front & back hold the pointers to front and rear end of the queue membes and count tracks the number of elements in the queue .

The rationale to utilize front and back members allows the queue to be circular queue within a linear array . Other way to implment same by copying the elements of array every time they are dequeued .

###### Code ####

#ifndef QUEUE_H
#define QUEUE_H

#include <string>

using namespace std;

/*
* QUEUESIZE should be one more than the desired queue size
* The queue will hold QUEUESIZE-1 elements
* The unused element is used to distinguish full versus empty
*/
const int QUEUESIZE = 11;

class queue
{
public:

queue();
void enqueue(string item);
string dequeue();
bool isFull() const;
bool isEmpty() const;

private:

// TODO: implement the private member as described in the specification
int front;
int back;
int count ;
string list[QUEUESIZE];
};

#endif

### queue.cpp

#include "queue.h"
#include <iostream>

// Default constructor initialize membes to zeros
queue::queue()
{
this->front = 0;
this->back = 0;
this->count = 0 ;
}

void queue::enqueue( string item )
{

// add the element only if current count is < queuesize
if ( count < QUEUESIZE)
{

// add the element at back and increment the back counter and count
    list[back] = item;
    back = (back + 1) % QUEUESIZE;
    this->count += 1;
    std::cout << " Inserted " << item << " Count " << this->count << " F : " << front << " back " << back << " < " << QUEUESIZE << "\n";
}
}

string queue::dequeue()
{
//cout << " retrieving :: ";

// Retrieve the element only if count is > 0
if ( count > 0 )
{
    int idx = front ;

    // increment the front
    front = (front + 1 )% QUEUESIZE ;
    count -= 1;
    //cout << list[idx] << "Count : " << count << " Idx : " << idx << " F: " << front << " back : " << back << "\n";

    return list[idx];
}
return "";
}

bool queue::isEmpty() const
{
return (count == 0);
}

bool queue::isFull() const
{
   return ( count == QUEUESIZE);
}

##### Output #####