Deep copy of binary tree - c++

Question

I have this tree with different types of nodes that I need to do a deep copy on. The hierarchy looks something like this:
class AllNodes
{
//this is a purely virtual base class
};
class TreeNode : public AllNodes
{
AllNodes *rChild, *lChild;
};
class LeefNode : public AllNodes
{
int value;
};
The problem is that when I want to do a deep copy of the entire tree, I don't know what nodes will have children and what nodes will have values. I've tried this, but it wont work (for obvious reasons):
void AllNodes::deepCopy(AllNodes* &copied, AllNodes* o)
{
if(o->rChild == nullptr)
copied->rChild = nullptr;
else
{
copied->rChild = o->rChild;
deepCopy(copied->rchild, o->rChild);
}
if(o->lChild == nullptr)
copied->lChild = nullptr;
else
{
copied->lChild = o->lChild;
deepCopy(copied->lChild, o->lChild);
}
}
Does anyone have some ideas of how to accomplish this?

Answer 1

Create a virtual method and implement it in TreeNode and LeafNode.
class AllNodes
{
//this is a purely virtual base class
virtual AllNodes* copy() const = 0;
};
class TreeNode : public AllNodes
{
AllNodes* rChild, lChild;
virtual AllNodes* copy() const {
TreeNode *n = new TreeNode;
n->rChild = rChild->copy();
n->lChild = lChild->copy();
return n;
}
};
class LeafNode : public AllNodes
{
int value;
virtual AllNodes* copy() const {
LeafNode *n = new LeafNode;
n->value = value;
return n;
}
};
(Just a draft)

Answer 2

This is polymorphic behavior (creating a deep copy, based on the concrete type of the object). As such, it should be implemented in a virtual function, accross the entire nodes hierarchy.
The function to perform the deep copy is usually called clone:
class AllNodes
{
//this is a purely virtual base class
public:
virtual AllNodes* clone() = 0;
};
class TreeNode : public AllNodes
{
AllNodes *rChild, *lChild; // you skipped declaring lChild as a pointer
public:
virtual AllNodes* clone() override // recursive implementation for child nodes
{
return new TreeNode{
rChild ? rChild->clone() : nullptr,
lChild ? lChild->clone() : nullptr }; // assume existence of this
// constructor
}
};
class LeafNode : public AllNodes
{
int value;
public:
virtual AllNodes* clone() override
{
return new LeafNode{ value }; // assume existence of this constructor
}
};
Client code (deep copy of the entire tree):
AllNodes *original; // filled in elsewhere
AllNodes *deepCopy = original->clone();