list.cpp

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

void List::appendNode(int num)
{
    ListNode *newNode; //Points to new node
    ListNode *nodePtr; //Moves through the list

    //Allocates new node and stores num there:
    newNode = new ListNode;
    newNode->value = num;
    newNode->next = 0;

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

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

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

void List::insertNode(int num)
{
    ListNode *newNode; //Creates a new node
    ListNode *nodePtr; //To traverse the list
    ListNode *previousNode = 0; //The previous node

    //Allocates a new node and stores 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 = 0;
    }
    else
    {
        nodePtr = head; //Position nodePtr at the head of the list
        previousNode = 0;

        //Skip all nodes whose value is less than num
        while (nodePtr != 0 && nodePtr->value < num)
        {
            previousNode = nodePtr;
            nodePtr = nodePtr->next;
        }

        //If the new node is the 1st in the list insert it before other nodes
        if (previousNode == 0)
        {
            head = newNode;
            newNode->next = nodePtr;
        }
        else
        {
            previousNode->next = newNode;
            newNode->next = nodePtr;
        }
    }
}

void List::deleteNode(int num)
{
    ListNode *nodePtr;
    ListNode *previousNode;

    //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
    {
        nodePtr = head;

        //Skips all nodes whose value member is not equal to num:
        while (nodePtr != 0 && 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;
        }
    }
}

void List::displayList()
{
    ListNode *nodePtr = head;

    while(nodePtr != 0)
    {
        cout << nodePtr->value;
        if (nodePtr->next != 0)
            cout << "-->";
        nodePtr = nodePtr->next;
    }
}

List::~List()
{
    ListNode *nodePtr;
    ListNode *nextNode;

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

    //While nodePtr is not at the end of the list
    while (nodePtr != 0)
    {
        //Save a pointer to the next node
        nextNode = nodePtr->next;

        //Delete the current node
        delete nodePtr;

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