Priority Queue using DLL structure with information taken from sources listed plus help from Arielle Patrice, Bergen Community College

Priority Queue

//http://www.cprogramming.com/snippets/source-code/priority-queue-with-linked-list
//http://www.sanfoundry.com/cpp-program-implements-priority-queue/
//https://www.youtube.com/watch?v=yIUFT6AKBGE
//http://faculty.cs.niu.edu/~mcmahon/CS241/Notes/doubly_linked.html

#include<iostream>
#include<cstdlib>

using namespace std;

    
class DNode
{                                                     // Establish DNode Class
private:
    DNode *next;                                                // Node to use in list
    DNode *prev;
                                                                // Node element values
    int key;
    string name;
    string ff;
    double price;
    int time;
    friend class DLinkedList;                                   // Give access to DLinkedList
};

class DLinkedList
{
private:
    DNode *head;                                              // List Sentinels
    DNode *tail;
public:
    DLinkedList();                                              // Constructor
    ~DLinkedList();                                             // Destructor
    bool empty();                                         // Bool - is the list empty
    const int& front() const;                                // Get Front Element
    const int& back() const;                                 // Get Tail Element
    void insertBack(const int& k, const string& n, const string& f, const double& p, const int& t);
    void insert(const int& k, const string& n, const string& f, const double& p, const int& t);
    //void remove();
    void removeFront();
    void removeBack();
    void removeMin();
    void display();                                      // Display from Header

protected:
    void insert(DNode *v, const int& k, const string& n, const string& f, const double& p, const int& t);
    void remove(DNode *v);
};

bool DLinkedList::empty()
{   return(head-> next == tail); }

const int& DLinkedList::front() const
{   return head-> next-> key; }

const int& DLinkedList::back() const
{   return tail-> prev-> key; }
    
int ffPoints(string);
int price$$(double);
int arrivalTime(int);

int main ()
{
    DLinkedList list = DLinkedList();                           // create variabl
    int pkey = 0;
    int ffpkey;
    int ppkey;
    int tpkey;
    string name;
    string fflyer;
    double price;
    int time;
    char y;

    cout << "Please enter the following information." << endl;  // get input
    cout << "Name: ";
    cin >> name;
    cout << "Frequent Flyer Status:  ";
    cin >> fflyer;
    ffpkey = ffPoints(fflyer);
    cout << "ticket price paid:  ";
    cin >> price;
    ppkey = price$$(price);
    cout << "Check in time at gate in minutes: ";
    cin >> time;
    tpkey = arrivalTime(time);
    pkey = tpkey + ffpkey + ppkey;
    list.insertBack(pkey, name, fflyer, price, time);
    
    cout << "Do you want to add an passenger (Y/N): ";
    cin >> y;
    while(y == 'y' || y == 'Y')
    {
        cout << "Please enter the following information." << endl;  // get input
        cout << "Name: ";
        cin >> name;
        cout << "Frequent Flyer Status:  ";
        cin >> fflyer;
        ffpkey = ffPoints(fflyer);
        cout << "ticket price paid:  ";
        cin >> price;
        ppkey = price$$(price);
        cout << "Check in time at gate in minutes: ";
        cin >> time;
        tpkey = arrivalTime(time);
        pkey = tpkey + ffpkey + ppkey;
        list.insertBack(pkey, name, fflyer, price, time);
        cout << "Do you want to add an passenger (Y/N): ";
        cin >> y;
        cout << endl;
    }
    
    int choice;
    
    do
    {
        cout << "Enter the number for the selection you want: \n";
        cout << "1. Identify passenger with highest priority and remove from list.\n";
        cout << "2. Display names of remaining passengers.\n";
        cout << "3. Quit Program.\n";
        cout << endl;
        cout << "Enter your selection (1, 2, or 3): ";
        cin >> choice;
        while(choice < 1 || choice > 3)
        {
            cout << "The valid choices are 1 through 3.  Please\n"
            << "select one of those." << endl;
            cout << "Enter your selection: ";
            cin >> choice;
            cout << endl;
        }
        switch(choice)
        {
            case 1:                                                 // display function described below
                list.removeMin();
                cout << endl;
                break;
            case 2:                                                 // search function described below
                list.display();
                cout << endl;
                break;
            case 3:                                                 // ends program
                cout << "Thank you for using this program.\n";
                cout << endl;
        }
    }while(choice != 3);
    
    return 0;
}

DLinkedList::DLinkedList()
{
    head = new DNode;
    tail = new DNode;
    head-> next = tail;
    tail-> prev = head;
}

DLinkedList::~DLinkedList()
{
    while(!empty()) removeFront();
    delete head;
    delete tail;
}

void DLinkedList::remove(DNode * v)
{
    DNode *u = v-> prev;
    DNode *w = v-> next;
    u-> next = w;
    w-> prev = u;
    delete v;
}

void DLinkedList::removeFront()
{   remove(head-> next); }

void DLinkedList::removeBack()
{   remove(tail-> prev); }

void DLinkedList::removeMin()
{
    if(!empty())
    {
        DNode *minNode = head-> next;
        DNode *searchNode = head-> next;
        while(searchNode-> next != tail)
        {
            searchNode = searchNode-> next;
            if(searchNode-> key < minNode-> key)
            {
                minNode = searchNode;
            }
        }
        if(minNode-> prev != head)
        {
            if(minNode-> next != tail)
            {
                minNode-> prev-> next = minNode-> next;
                minNode-> next-> prev = minNode-> prev;
            }
            else
            {
                minNode-> prev-> next = tail;
                tail-> prev = minNode-> prev;
            }
        }
        else
        {
            minNode-> next-> prev = head;
            head-> next = minNode-> next;
        }
        cout << "Customer with highest priority key is: " << endl;
        cout << minNode-> key << " " << minNode-> name << " " << minNode-> ff << " " << minNode-> price << " " << minNode-> time << endl;
        cout << "Customer name has been removed from the list" << endl;
        delete(minNode);
        cout << endl;
    }
    else
    {
        cout << "The list is empty." << endl;
    }
}

void DLinkedList::insert(DNode* v, const int& k, const string& n, const string& f, const double& p, const int& t)
{
    DNode *u = new DNode;
    u-> key = k;
    u-> name = n;
    u-> ff = f;
    u-> price = p;
    u-> time = t;
    u-> next = v;
    u-> prev = v-> prev;
    u-> prev-> next = u;
    v-> prev = u;
}

void DLinkedList::insertBack(const int& k, const string& n, const string& f, const double& p, const int& t)
{   insert(tail, k, n, f, p, t); }

void DLinkedList::display()
{
    DNode* temp = head-> next;
    if(empty())
        cout << "Queue is empty" << endl;
    else
    {
        while (temp != tail)
        {
            cout << temp-> key << " " << temp-> name << " " << temp-> ff << " " << temp-> price << " " << temp-> time << endl;
            temp = temp-> next;
        }
    }
    cout << endl;
}



int k;

int ffPoints(string status)
{
    if(status == "PLAT")
        k = 0;
    else if(status == "GOLD")
        k = 20;
    else if(status == "SLVR")
        k = 30;
    else
        k = 40;
    return k;
}

int price$$(double pricePaid)
{
    if (pricePaid >= 500)
        k = 0;
    else if(pricePaid < 500 && pricePaid >= 450)
        k = 5;
    else if(pricePaid < 450 && pricePaid >= 400)
        k = 10;
    else if(pricePaid < 400 && pricePaid >= 350)
        k = 15;
    else if(pricePaid < 350 && pricePaid >= 300)
        k = 20;
    else if(pricePaid < 300 && pricePaid >= 250)
        k = 25;
    else if(pricePaid < 250 && pricePaid >= 200)
        k = 30;
    else if(pricePaid< 200 && pricePaid >= 150)
        k = 35;
    else if(pricePaid < 150 && pricePaid >= 100)
        k = 40;
    else if(pricePaid < 100 && pricePaid >= 50)
        k = 45;
    else
        k = 50;
    return k;
}

int arrivalTime(int min)
{
    if(min >= 60)
        k = 0;
    else
        k = 60 - min;
    return k;
}