HashMap Implementation - 0x0000005 Error

[ZotIc]

Hi,
This is my first post on this forum! :)
I have been trying to implement a HashMap in C++, but I keep getting the "Process returned -1073741819 (0xC0000005)" error.
I don't get that error every single execution, but I get it frequently - that is the program sometimes executes successfully, and the rest of the time I get the error as stated above.

My code:

#include<iostream>
#include<cstdlib>

using namespace std;

class Link{
public:
    int iData;
    Link *next;
public:
    Link(int d): iData(d)
    { }

    int getKey(){return iData;}

    void displayLink(){
        cout<<iData<<" ";
    }
};

class HashList{
public:
    Link *first;
public:
    HashList(): first(NULL)
    { }

    void insertItem(Link data){
        int key = data.getKey();
        Link *previous = NULL;
        Link *current = first;
        while(current!=NULL && key > current->getKey()){
            previous = current;
            current = current->next;
        }
            Link *t = (Link*)malloc(sizeof(Link));
            t->iData = data.iData;
        if(previous==NULL){
            first = t;
        }
        else{
            previous->next = t;
        }
        t->next = current;
    }

    void deleteItem(int key){
        Link *previous = NULL;
        Link *current = first;
        while(current!=NULL && key != current->getKey()){
            previous = current;
            current = current->next;
        }

        if(previous == NULL){
            first = first->next;
        }
        else{
            previous->next = current->next;
        }
    }

    void findItem(int key){
        Link *current = first;
        while(current!=NULL && current->getKey()<=key){
            if(current->getKey()==key){
                cout<<"Item found!"<<endl;
                return;
            }
            current = current->next;
        }
        cout<<"Item not found!"<<endl;
    }

    void displayList(){
        cout<<"List: first->last"<<endl;
        Link *current = first;
        while(current!=NULL){
            current->displayLink();
            current = current->next;
        }
        cout<<""<<endl;
    }
};


class HashTable{
public:
    int size;
    HashList *hLink = (HashList*)malloc(size*sizeof(HashList));
public:
    HashTable(int arrsize){
        size = arrsize;
        int i;
        for(i = 0;i<size;i++){

            hLink[i] = HashList();
        }
    }

    void displayTable(){
        int i;
        for(i = 0;i<size;i++){
            cout<<i<<". ";
            hLink[i].displayList();
        }
    }

    int hashFunction(int key){return key%size;}

    void insertData(Link d){
        int key = d.getKey();
        int hashVal = hashFunction(key);
        cout<<"hash value for item to be added is: "<<hashVal<<endl;
        hLink[hashVal].insertItem(d);
    }

    void deleteData(int key){
        int hashVal = hashFunction(key);
        cout<<"hash value for item to be deleted is: "<<hashVal<<endl;
        hLink[hashVal].deleteItem(key);
    }

    void find(int key){
        int hashVal = hashFunction(key);
        cout<<"hash value for item to be searched is: "<<hashVal<<endl;
        hLink[hashVal].findItem(key);
    }


};



int main(){
    Link a(12);
    Link b(32);
    Link c(82);
    Link d(55);
    Link e(89);

    HashTable h(10);
    h.insertData(a);
    h.insertData(b);
    h.insertData(c);
    h.deleteData(12);

    h.displayTable();

    h.find(11);
    h.find(32);
}

My guess is that the error is from one of the pointers, so I tried messing with the pointers and still I get the same error.
Also, can someone please explain why the program executes and gives the desired output sometimes but is still able to give an error when executed some other time?..

EDIT:
I may have found the error.The error seems to come from the memory allocation for the HashList.

HashList *hLink = (HashList*)malloc(size*sizeof(HashList));

If I try to use something like

HashList hLink[10];

and just call the class as HashTable foo, it works well - no errors.
Is there any proper way that I can dynamically allocate memory for the hashtable?

[AbstractionAnon]

Several things I see that are wrong:

Line 11 - Your constructor for Link doesn't initialize the pointer next. It's contents are going to be undefined.

Line 90 - size is uninitialized at the time this is executed. You're going to get a random size. Note that 93 is not executed until AFTER the members of the class have been initialized.

can someone please explain why the program executes and gives the desired output sometimes but is still able to give an error when executed some other time?..

When you're referencing undefined memory, it's a wonder your program executes at all.

[cire]

In addition to what AbstractionAnon has said, your constructor for Link will not be invoked unless you use placement new on the memory you have malloc'd. Is there some reason you're not using new in place of malloc?

You don't free any memory. Ever. Please do.

If you call HashList::deleteItem on an empty HashList, you will dereference a nullptr.

[ZotIc]

Thank you for your replies!
I fixed the constructor of Link class and declared HashTable as
hLink = new HashTable[size]; and it works fine!
I did try using new at some point but, it didn't work out at that time(maybe due to some other pointer or memory error).Now after fixing all those stuff I totally forgot about the new!
About freeing memory.. I will keep that in mind :) .Thanks again!