Week 7: Assignment - Circular or Doubly Linked Lists
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cmake_minimum_required(VERSION 3.16)
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project(week-07)
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set(CMAKE_CXX_STANDARD 17)
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add_executable(week-07 main.cpp)
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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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* Champlain College SDEV-345-81
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*
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* C++ Week 6: Circular or Doubly Linked Lists (first semester) - Linked Lists program (2020/10/16)
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*
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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*
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* Write a menu driven program that creates a doubly linked list.
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* The program should give the user the following options and should
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* run in an infinite loop:
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* 1) Insert first node
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* 2) Insert last node
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* 3) Delete first node
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* 4) Delete last node
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* 5) Display list forward
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* 6) Display list backwards
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*
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* Do not use the C++ Standard template library.
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*
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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*
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* Written by Llewellyn van der Merwe <llewellyn.vandermerw@mymail.champlain.edu>, October 2020
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* Copyright (C) 2020. All Rights Reserved
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* License GNU/GPL Version 2 or later - http://www.gnu.org/licenses/gpl-2.0.html
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*
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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// Adaptation to the code found at
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// Week 7: Lecture 4 - Doubly Linked CPP
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// Demonstrates Doubly Linked Lists
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#include <iostream>
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using namespace std;
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////////////////////////////////////////////////////////////////
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class Link
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{
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public:
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double dData; // data item
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Link* pNext; // next link in list
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Link* pPrevious; // previous link in list
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public:
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//-------------------------------------------------------------
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Link(double dd) : // constructor
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dData(dd), pNext(NULL), pPrevious(NULL)
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{ }
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//-------------------------------------------------------------
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void displayLink() // display this link
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{ cout << dData << " "; }
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//-------------------------------------------------------------
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}; //end class Link
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////////////////////////////////////////////////////////////////
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class DoublyLinkedList
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{
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private:
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Link* pFirst; // pointer to first item
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Link* pLast; // pointer to last item
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public:
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//-------------------------------------------------------------
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DoublyLinkedList() : // constructor
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pFirst(NULL), pLast(NULL)
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{ }
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//-------------------------------------------------------------
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~DoublyLinkedList() // destructor (deletes links)
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{
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Link* pCurrent = pFirst; // start at beginning of list
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while(pCurrent != NULL) // until end of list,
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{
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Link* pOldCur = pCurrent; // save current link
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pCurrent = pCurrent->pNext; // move to next link
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delete pOldCur; // delete old current
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}
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}
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//-------------------------------------------------------------
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bool isEmpty() // true if no links
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{ return pFirst==NULL; }
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//-------------------------------------------------------------
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void insertFirst(double dd) // insert at front of list
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{
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Link* pNewLink = new Link(dd); // make new link
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if( isEmpty() ) // if empty list,
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pLast = pNewLink; // newLink <-- last
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else
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pFirst->pPrevious = pNewLink; // newLink <-- old first
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pNewLink->pNext = pFirst; // newLink --> old first
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pFirst = pNewLink; // first --> newLink
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}
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//-------------------------------------------------------------
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void insertLast(double dd) // insert at end of list
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{
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Link* pNewLink = new Link(dd); // make new link
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if( isEmpty() ) // if empty list,
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pFirst = pNewLink; // first --> newLink
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else
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{
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pLast->pNext = pNewLink; // old last --> newLink
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pNewLink->pPrevious = pLast; // old last <-- newLink
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}
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pLast = pNewLink; // newLink <-- last
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}
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//-------------------------------------------------------------
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void removeFirst() // remove first link
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{ // (assumes non-empty list)
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Link* pTemp = pFirst;
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if(pFirst->pNext == NULL) // if only one item
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pLast = NULL; // null <-- last
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else
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pFirst->pNext->pPrevious = NULL; // null <-- old next
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pFirst = pFirst->pNext; // first --> old next
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delete pTemp; // delete old first
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}
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//-------------------------------------------------------------
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void removeLast() // remove last link
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{ // (assumes non-empty list)
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Link* pTemp = pLast;
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if(pFirst->pNext == NULL) // if only one item
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pFirst = NULL; // first --> null
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else
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pLast->pPrevious->pNext = NULL; // old previous --> null
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pLast = pLast->pPrevious; // old previous <-- last
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delete pTemp; // delete old last
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}
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//-------------------------------------------------------------
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void displayForward()
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{
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cout << "List (first-->last): ";
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Link* pCurrent = pFirst; // start at beginning
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while(pCurrent != NULL) // until end of list,
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{
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pCurrent->displayLink(); // display data
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pCurrent = pCurrent->pNext; // move to next link
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}
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cout << endl;
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}
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//-------------------------------------------------------------
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void displayBackward()
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{
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cout << "List (last-->first): ";
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Link* pCurrent = pLast; // start at end
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while(pCurrent != NULL) // until start of list,
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{
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pCurrent->displayLink(); // display data
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pCurrent = pCurrent->pPrevious; // go to previous link
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}
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cout << endl;
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}
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//-------------------------------------------------------------
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}; //end class DoublyLinkedList
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////////////////////////////////////////////////////////////////
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void getUserInput(const string &question, double &value) {
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cin.clear();
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while (true) {
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cout << question << endl;
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cout << "[value]: ";
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cin >> value; // get only an double
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if (!cin.fail() && value > 0) {
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cin.ignore(numeric_limits<streamsize>::max(), '\n');
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break;
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}
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cin.clear();
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cin.ignore(numeric_limits<streamsize>::max(), '\n');
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cout << "The value must be an double above zero, lets try again." << endl;
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}
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}
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void displayMenu(int &action) {
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while (true) {
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cin.clear();
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cout << " 1] Insert first node" << endl;
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cout << " 2] Insert last node" << endl;
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cout << " 3] Delete first node" << endl;
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cout << " 4] Delete last node" << endl;
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cout << " 5] Display list forward" << endl;
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cout << " 6] Display list backwards" << endl;
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cout << " [1-6]: ";
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cin >> action;
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action = (int) action;
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if (!cin.fail() && action > 0 && action < 7) {
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break;
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}
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cin.clear();
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cin.ignore(numeric_limits<streamsize>::max(), '\n');
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cout << "Selection must be between 1 and 6, lets try again." << endl;
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}
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}
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////////////////////////////////////////////////////////////////
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int main()
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{
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DoublyLinkedList theList; // make a new list
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int action; // the driver action
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double data; // the driver double Data
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cout << "Demonstrating the infinite doubly linked list program" << endl; // little notice
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while (true) {
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displayMenu(action); // display the menu
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if (action == 1) { // Insert first node
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getUserInput("Enter a number", data);
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theList.insertFirst(data);
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} else if (action == 2) { // Insert last node
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getUserInput("Enter a number", data);
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theList.insertLast(data);
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} else if (action == 3) { // Delete first node
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if (!theList.isEmpty()) {
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theList.removeFirst();
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} else {
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cout << "The doubly linked list is empty, can not remove any items." << endl;
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}
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} else if (action == 4) { // Delete last node
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if (!theList.isEmpty()) {
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theList.removeLast();
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} else {
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cout << "The doubly linked list is empty, can not remove any items." << endl;
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}
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} else if (action == 5) { // Display list forward
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if (!theList.isEmpty()) {
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theList.displayBackward();
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} else {
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cout << "The doubly linked list is empty, no items to display backward." << endl;
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}
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} else if (action == 6) { // Display list backwards
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if (!theList.isEmpty()) {
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theList.displayForward();
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} else {
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cout << "The doubly linked list is empty, no items to display forward." << endl;
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}
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} else {
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break; // just to remove endless loop warning (should never happen)
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}
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}
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return 0;
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}
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