numberlist.cpp

// Implementation file for the NumberList class
#include <iostream>  // For cout  and NULL
#include "NumberList.h"
using namespace std;

//**************************************************
// appendNode appends a node containing the        *
// value pased into num, to the end of the list.   *
//**************************************************

void NumberList::appendNode(int num)
{
	ListNode *newNode;  // To point to a new node
	ListNode *nodePtr;  // To move through the list

	// Allocate a new node and store num there.
	newNode = new ListNode;
	newNode->value = num;
	newNode->next = NULL;

	// If there are no nodes in the list
	// make newNode the first node.
	if (!head)
		head = newNode;
	else  // Otherwise, insert newNode at end.
	{
		// Initialize nodePtr to head of list.
		nodePtr = head;

		// Find the last node in the list.
		while (nodePtr->next)
			nodePtr = nodePtr->next;

		// Insert newNode as the last node.
		nodePtr->next = newNode;
	}
}

//**************************************************
// displayList shows the value                     *
// stored in each node of the linked list          *
// pointed to by head.                             *
//**************************************************

void NumberList::displayList() const
{
	ListNode *nodePtr;  // To move through the list

	// Position nodePtr at the head of the list.
	nodePtr = head;

	// While nodePtr points to a node, traverse
	// the list.
	while (nodePtr)
	{
		// Display the value in this node.
		cout << nodePtr->value << endl;

		// Move to the next node.
		nodePtr = nodePtr->next;
	}
}

//**************************************************
// The insertNode function inserts a node with     *
// num copied to its value member.                 *
//**************************************************

void NumberList::insertNode(int num)
{
	ListNode *newNode;             // A new node
	ListNode *nodePtr;             // To traverse the list
	ListNode *previousNode = NULL; // The previous node

	// Allocate a new node and store num there.
	newNode = new ListNode;
	newNode->value = num;

	// If there are no nodes in the list
	// make newNode the first node
	if (!head)
	{
		head = newNode;
		newNode->next = NULL;
	}
	else  // Otherwise, insert newNode
	{
		// Position nodePtr at the head of list.
		nodePtr = head;

		// Initialize previousNode to NULL.
		previousNode = NULL;

		// Skip all nodes whose value is less than num.
		while (nodePtr != NULL && nodePtr->value < num)
		{
			previousNode = nodePtr;
			nodePtr = nodePtr->next;
		}

		// If the new node is to be the 1st in the list,
		// insert it before all other nodes.
		if (previousNode == NULL)
		{
			head = newNode;
			newNode->next = nodePtr;
		}
		else  // Otherwise insert after the previous node.
		{
			previousNode->next = newNode;
			newNode->next = nodePtr;
		}
	}
}

//**************************************************
// The deleteNode function searches for a node     *
// with num as its value. The node, if found, is   *
// deleted from the list and from memory.          *
//**************************************************

void NumberList::deleteNode(int num)
{
	ListNode *nodePtr;       // To traverse the list
	ListNode *previousNode;  // To point to the previous node

	// If the list is empty, do nothing.
	if (!head)
		return;

	// Determine if the first node is the one.
	if (head->value == num)
	{
		nodePtr = head->next;
		delete head;
		head = nodePtr;
	}
	else
	{
		// Initialize nodePtr to head of list
		nodePtr = head;

		// Skip all nodes whose value member is
		// not equal to num.
		while (nodePtr != NULL && nodePtr->value != num)
		{
			previousNode = nodePtr;
			nodePtr = nodePtr->next;
		}

		// If nodePtr is not at the end of the list,
		// link the previous node to the node after
		// nodePtr, then delete nodePtr.
		if (nodePtr)
		{
			previousNode->next = nodePtr->next;
			delete nodePtr;
		}
	}
}

//**************************************************
// Destructor                                      *
// This function deletes every node in the list.   *
//**************************************************

NumberList::~NumberList()
{
	ListNode *nodePtr;   // To traverse the list
	ListNode *nextNode;  // To point to the next node

	// Position nodePtr at the head of the list.
	nodePtr = head;

	// While nodePtr is not at the end of the list...
	while (nodePtr != NULL)
	{
		// Save a pointer to the next node.
		nextNode = nodePtr->next;

		// Delete the current node.
		delete nodePtr;

		// Position nodePtr at the next node.
		nodePtr = nextNode;
	}
}