Binary Tree Deserialization

[Numeri]

So as a learning exercise, I am trying to read and write a binary tree to a file. After googling around, I decided to use a preorder traversal (including null nodes) to write the binary tree to the file. I got stuck trying to read a tree from a file. I can't figure out how to create an unknown number of nodes when they are needed. I could use an array, but that just seems bulky - plus it could run out of space. Is that what I have to do? I've heard of vectors before, but not very much. Are they more appropriate for this situation?

Thanks,
Numeri

[Peter87]

Can't you create the nodes when you need them, while traversing?

[Numeri]

Sorry for being unclear - that's exactly my problem - I don't know how. What would I 'name' each node?

Thanks!
Numeri

[Peter87]

name? Do they need a name? I was thinking you could create the nodes with new.

[Numeri]

I just read about the new operator here: http://www.cplusplus.com/reference/new/operator%20new/ . Based on it, I think I should do this.

//...
new (curNode.lChild) node;
//...
curNode = *curNode.lChild;
//... 

Would that work? (Sorry, I've just started learning about pointers recently.)

Thank you,
Numeri

[Numeri]

Another question, really quick, why is this code:

string wBinTree(node *p)
{
	string str = "";
	if (!p)
	{
		str += "# ";
	}
	else
	{
		str += p->data + " ";
		str += (wBinTree(p->lChild)+wBinTree(p->rChild));
		return str;
	}
}

giving me this error:

Unhandled exception at 0x75f3c41f in ... std::length_error at memory location 0x0025ef04..

I'm compiling with Visual Studio 2010.

Thanks,
Numeri

EDIT:
I'm an idiot, sorry. I accidently put the return inside the else statement.