排序算法在试图打印列表信息时崩溃

在我的应用程序中，我想排序对象升序和降序。为此，我写了3个函数。它可能排序，但当我想打印所有的列表，我有错误，如:访问违反读取位置0x00000000。我想名单是空的，但我不确定。有什么问题吗?总而言之:排序后List似乎是空的。算法可以工作，但是打印列表的函数崩溃了。

JednostkaMaszyny是一个基本的抽象类。

//此函数负责查找列表中最大和最小的ID并返回其值。

int static findID(JednostkaMaszyny*& headOfList, short numberOfObjects,bool ascending)
{
    short i = 0;
    int IDtoFind = 0;
    JednostkaMaszyny* iterator;
    iterator = headOfList;

    /*if(rosnaco)
    {
        IDtoFind = 999999999;
    }
    else
    {
        IDtoFind = 0;
    }*/

    while(i < numberOfObjects)
    {
        if(!ascending){
            if(iterator->getID() > IDtoFind)
            {
                IDtoFind = iterator->getID();
            }
            //i++;
            //iterator = iterator->nextObject;
        }
        else
        {
            if(iterator->getID() < IDtoFind)
            {
                IDtoFind = iterator->getID();
            }

        }
        i++;
            iterator = iterator->nextObject;
    }
    return IDtoFind;
};

该函数接受指向主列表的指针、列表中当前对象的个数和ID。

static JednostkaMaszyny*& getObjectAtIDAndAssignItToSortedList(JednostkaMaszyny*& headOfList, short numberOfObjects, int ID)
{
    short i = 0;
    JednostkaMaszyny* iterator;
    JednostkaMaszyny* returnedObject = NULL;
    int tmpBoolNumber;
    bool tmpBool = false;
    iterator = headOfList;
    while(i < iloscObiektow)
    {
        tmpBoolNumber = iterator->getBoolSorted();
        if((iterator->getID() == ID) && tmpBoolNumber)
        {
            cout<<iterator->getID();
            if(typeid(*iterator) == typeid(Desktop))
            {
                 returnedObject = new Desktop(((Desktop*)iterator)->getwysokosc(),((Desktop*)iterator)->getDlugosc(),((Desktop*)iterator)->getSzerokosc(),((Desktop*)iterator)->getClockProcessor()
                     ,((Desktop*)iterator)->getIdNumber(),((Desktop*)iterator)->getprocessorType(),((Desktop*)iterator)->getnameInNetwork(),((Desktop*)iterator)->getID());
                //((Desktop*)iterator) -> setBoolSorted(1);
                break;
            }
            else
            {
                returnedObject = new Laptop(((Laptop*)iterator)->getWagaLaptopa(),((Laptop*)iterator)->getClockProcessor(),((Laptop*)iterator)->getIdNumber(),((Laptop*)iterator)->getprocessorType(),
                    ((Laptop*)iterator)->getnameInNetwork(),((Laptop*)iterator)->getID());
                //((Laptop*)iterator) -> setBoolSorted(1);
                break;
            }
            iterator->setBoolSorted(1);
        }
        i++;
        iterator = iterator->nextObject;
    }
    //iterator->setID(1); I've tried to set attribute of object that it is already sorted but it fails here saying: Access fail to object.......
    return returnedObject;
};

最后一个函数。它是主要的"引擎"。它接受指向主列表的指针，对象数和指向列表中最后一个对象的有用指针。

void static sortListByUser(JednostkaMaszyny*& headOfList, short numberObjects, JednostkaMaszyny*& helpFullPointer)
{
    JednostkaMaszyny* tmpSortedList = NULL;
    JednostkaMaszyny* iterator;
    short choice;
    short numberOfObjects;
    int tmpId;
    numberOfObjects = numberObjects;
    cout<<"1 - Ascending"<<endl;
    cout<<"2 - Descending"<<endl;
    cout<<"Your choice: "; cin>>choice;
    if(choice == 1)
    {
        if(numberOfObjects > 0)
        {
            while(numberOfObjects > 0)
            {
                if(tmpSortedList == NULL)
                {
                    tmpId = findID(headOfList,numberOfObjects,false);
                    tmpSortedList = getObjectAtIDAndAssignItToSortedList(headOfList,numberOfObjects,tmpId);
                    iterator = tmpSortedList;
                    //tmpSortedList->previousObject = NULL;
                    numberOfObjects--;
                }
                else
                {
                    tmpId = findID(headOfList,numberOfObjects,false);
                    iterator->nextObject = getObjectAtIDAndAssignItToSortedList(headOfList,numberOfObjects,tmpId);
                    iterator->nextObject->previousObject = iterator;
                    iterator = iterator->nextObject;
                    numberOfObjects--;
                }
                //iterator->nextObject = NULL;
            }
            //iterator->
        }
        else
        {
            cout<<"LISTA JEST PUSTA"<<endl<<endl;
        }
    }
};