Copying a binary tree - binary-tree

Question

When asked to create a copy of the binary tree, I have always been told to use a post order traversal logic to make the copy.
Is it not possible to process the original tree in pre-order or in-order to create a copy?
Any traversal method more optimal than the other?
Post-order way:
NODEPTR Copy(NODEPTR p)
{
if (p == null) return p
NODEPTR left = Copy(p-> left)
NODEPTR right = Copy(p-> right)
NODEPTR root = MakeBT(p->data, left, right) //MakeBT is a helper function that makes a tree
return (root)
}
Pre-order way:
NODEPTR Copy(NODEPTR p)
{
if (p == null) return p
NODEPTR root
root->data = p->data
root-> left = Copy(p-> left)
root-> right = Copy(p-> right)
return (root)
}
In-order way:
NODEPTR Copy(NODEPTR p)
{
if (p == null) return p
NODEPTR left = Copy(p-> left)
NODEPTR root
root-> data = p-> data
root-> left = left
root-> right = Copy(p-> right)
return (root)
}

Answer 1

Here is a cpp program to copy a binary tree(Node) to a new binary tree(NewNode).
#include <iostream>
using namespace std;
class Node{
public:
int val;
Node* left=NULL;
Node* right=NULL;
Node(int val){
this->val=val;
this->right=NULL;
this->left=NULL;
}
void insert(int v){
if(this->left==NULL)
this->left=new Node(v);
else if(this->right==NULL)
this->right=new Node(v);
else
cout<<"impossible to insert the node\n";
}
void print(){
cout<<this->val<<" ";
if(this->left) this->left->print();
if(this->right) this->right->print();
}
};
class NewNode{
public:
int val;
NewNode* left=NULL;
NewNode* right=NULL;
NewNode* parent=NULL;
void print(){
cout<<this->val<<" ";
if(this->left) this->left->print();
if(this->right) this->right->print();
}
};
void copy(Node* original,NewNode* duplicate){
duplicate->val=original->val;
// cout<<duplicate->val<<endl;
if(original->left){
NewNode* newLeft=new NewNode;
newLeft->parent=duplicate;
duplicate->left=newLeft;
// printf("in left copying %d %d %d\n",duplicate->val,duplicate->left,duplicate->parent);
copy(original->left,duplicate->left);
}
if(original->right){
NewNode* newRight=new NewNode;
newRight->parent=duplicate;
duplicate->right=newRight;
// printf("in right copying %d %d %d\n",duplicate->val,duplicate->right,duplicate->parent);
copy(original->right,duplicate->right);
}
}
int main(){
Node root(1);
root.insert(2);
root.insert(3);
printf("%d %d %d\n",root.val,root.left,root.right);
Node* temp=root.left;
temp->insert(4);
temp->insert(5);
printf("%d %d %d\n",temp->val,temp->left,temp->right);
NewNode root2;
copy(&root,&root2);
printf("%d %d %d\n",root2.val,root2.left,root2.right);
NewNode *temp1=root2.left;
printf("%d %d %d\n",temp1->val,temp1->left,temp1->right);
root.print();
cout<<endl;
root2.print();
return 0;
}