// Lab Sheet 5 Example A (Class-based solution to Lab Problem 4.1)

// CS211 ADS2

// T Naughton, CS NUIM

#include<iostream>



/* This program reads positive integers, one per line, from the

** keyboard into a list. The user indicates that they are finished

** by entering any negative integer (the negative integer itself is

** not stored). The computer program then prints out the list of

** numbers, on a single line, separated with blank spaces. This

** program uses classes and a linked list.

*/



class ListElement {

  // A very simple class describing each node of the list

 public:

  int element;

  ListElement * next;

};



class IntList {



  ListElement * head; // a pointer to the head of the list



 public:

  IntList(); // constructor

  ~IntList(); // destructor



  // methods that act on IntList

  void AddtoFront(int newdata);

  void PrintList();

};



IntList::IntList() {

  head = NULL; // Initialise the list (mark the end of the list

               // with NULL).

}



IntList::~IntList() {

  // The entire list should be deleted here

}



void IntList::AddtoFront(int newdata){

  // This function creates a new node with that data that is passed to

  // it, adding the node to the front of the list.

  ListElement * temp;      // Create a pointer to a new node

  temp = new ListElement;  // Allocate memory for the node

  temp->element = newdata; // Put the data in the node



  // Put this node at the top of the list by (a) pointing it at the

  // head of the list and (b) repointing the head of the list at this

  // node.

  // Can you see that the first time we add a node to the list

  // (i.e. when head==NULL) that we end up marking the end of the

  // list with a NULL?

  temp->next = head;

  head = temp;

}



void IntList::PrintList(){

  // This function prints out the list. It does so by printing out the

  // contents of the head of the list and then each subsequent element

  // in turn. It repeats this until the end of the

  // list (a NULL) is found. The function returns a pointer to the

  // head of the list. Note: this function will work if an empty

  // list is passed to it.

  ListElement * current;

  current = head; // set current to point to the head of the list



  cout << endl << endl << "Here's the list:" << endl;

  while (current != NULL) {

    cout << current->element << ' ';

    current = current->next;

  }

}



void main(void){



  IntList list;



  int tempint; // temporary storage for ints from user



  cout << endl << endl << "Please enter positive integers (one ";

  cout << "per line). Terminate with any negative integer:" << endl;

  cin >> tempint;



  while (tempint >= 0) {

    list.AddtoFront(tempint);

    cin >> tempint;

  }



  list.PrintList();

}