access violation file handling URGENT HELP NEEDED PLZ :(

[ybkG1hU5]

Write your question here.
kindly review the code ive written. It's giving breaks. plz reply guys! it's EXTREMELY urgent :'(

  #include <iostream>
#include <string>
#include <fstream>
#define N 5 //works for 3 lettered, 4 lettered, 5 lettered, 6 lettered & 7 lettered words
using namespace std;

struct node 
{
	string imageid, ans;
	node *next;
};

static node *ChainedHashTable[N];

class Questions
{
private: 
	node *curr;
public:
	Questions();
	~Questions();
	void hashtable(node *);
	int getkey(node *);
	void read(int);
	void write();
	void displayall();
	void display(node*);

};

Questions::~Questions()
{
	for (int i=0; i<N; i++)
     {
       node *curr = ChainedHashTable[i];
       while (curr != NULL)
       {
         node *discard = curr;
		 curr=curr->next;
		 delete discard;
	   }
	}
	//delete []ChainedHashTable;
}
Questions::Questions()
{
	curr = NULL;

for(int i=0; i<N; i++)
{
	ChainedHashTable[i]= NULL;
}
	    write();
  /*  node *temp=new node;
	ofstream Write("D:\\quiz.txt", ios::binary|ios::app);
	if ( !Write.is_open() )
	{
		cout<<":(";
	}
	temp->ans="cross";
	temp->imageid="1.jpg";
	Write.write(reinterpret_cast<char*>(temp), sizeof(node));*/

		node temp1;
		ifstream Read("D:\\quiz.txt", ios::binary| ios::app);
		Read.seekg(0,ios::beg); 
		Read.read(reinterpret_cast<char*>(&temp1),sizeof(node));
		while(!Read.eof())
		{
			cout<<temp1.ans;
			hashtable(&temp1);
			Read.read(reinterpret_cast<char*>(&temp1),sizeof(node));
		}
		Read.close();
		cout<<"YOUR PROGRAM IS RUNNING FINE ALHAMDULILLAH :)";
		//displayall();
}

int Questions:: getkey(node *a)
{return a->ans.length(); - 3;}


	void Questions:: hashtable(node *a)
	{ 
		int key = getkey(a);

		if (ChainedHashTable[key] == NULL)
		{
			ChainedHashTable[key] = new node;
			ChainedHashTable[key]->ans=a->ans;
			ChainedHashTable[key]->imageid=a->imageid;
			ChainedHashTable[key]->next=NULL;
		}

		else 
	   {
		 node *temp1= ChainedHashTable[key];
         while(temp1->next)
	   {                           
		   // scrolls down the list
			temp1 = temp1->next;
       }
		    node *temp= new node;// inserst the value as the last element of the list
			temp1->next=temp;
			temp->ans=a->ans;
			temp->imageid=a->imageid;
			temp->next = NULL;
		}
	}


	void Questions:: displayall()
	{
		for (int i = 0; i < N; i++)
		{
			cout<< i + 3 << "Letters! "<<endl;
			display(ChainedHashTable[i]);
		}
	}

	void Questions:: write() 
	{
	node *temp=new node;
	ofstream Write("D:\\quiz.txt", ios:: binary|ios::app);
	if ( !Write.is_open() )
	{
		cout<<":(";
	}
	temp->ans="crosscutter";
	temp->imageid="1.jpg";
	Write.write(reinterpret_cast<char*>(&temp), sizeof(node));
	temp->ans="signatures";
	temp->imageid="2.jpg";
	Write.write(reinterpret_cast<char*>(temp), sizeof(node));
	temp->ans="imaan";
	temp->imageid="3.jpg";
	Write.write(reinterpret_cast<char*>(temp), sizeof(node));
	temp->ans="mona";
	temp->imageid="4.jpg";
	Write.write(reinterpret_cast<char*>(temp), sizeof(node));
	temp->ans="ma";
	temp->imageid="5.jpg";
	Write.write(reinterpret_cast<char*>(temp), sizeof(node));
	Write.close();
	}

void Questions:: display(node *p)
	{
		while (p != NULL)
		{
			cout << p->ans << endl;
			p = p->next;
		}
	
	}
			

int main()
{
	Questions test;
	system ("PAUSE");
	return 0;
}

[MiiNiPaa]

temp is a pointer. You are saving the same value of pointer 5 times in a row. And you should never save pointer values, as the are different each program execution.

And this is not to mention you are writing pointer, but expect to read node itself.

[ybkG1hU5]

Thank you SO much :D :D :D

[ybkG1hU5]

but it's still giving breakssss! :'( uwaaaaaaain

[MiiNiPaa]

So, what your code looks like now?

[ybkG1hU5]

void Questions:: write()
{
node temp;
ofstream Write("D:\\quiz.txt", ios:: binary|ios::app);
if ( !Write.is_open() )
{
cout<<":(";
}
temp.ans="crosscutter";
temp.imageid="1.jpg";
Write.write(reinterpret_cast<char*>(&temp), sizeof(node));
temp.ans="signatures";
temp.imageid="2.jpg";
Write.write(reinterpret_cast<char*>(&temp), sizeof(node));
temp.ans="imaan";
temp.imageid="3.jpg";
Write.write(reinterpret_cast<char*>(&temp), sizeof(node));
temp.ans="mona";
temp.imageid="4.jpg";
Write.write(reinterpret_cast<char*>(&temp), sizeof(node));
temp.ans="ma";
temp.imageid="5.jpg";
Write.write(reinterpret_cast<char*>(&temp), sizeof(node));
Write.close();
}

[MiiNiPaa]

string imageid, ans; Objects of complex (not TriviallyCopyable) types cannot be saved by simple call to .write(). You need to serialize them separately.

I suggest to drop binary here an serialize as text.

[ybkG1hU5]

you mean i should save them in a txt file?

[MiiNiPaa]

NO, I mean that you do not need to use write() and binary mode.
File extension is irrelevant.

Something like that:

void node::save(std::ostream& out)
{
    out << imageid << '\n' << ans << '\n';
}

node node::load(std::istream& in)
{
    node temp;
    std::getline(in, temp.imageid);
    std::getline(in, temp.ans    );
    return temp;
}

[ybkG1hU5]

got it got it. Thanks a lot @MiiNiPaa :)