data structure binary search tree

#include<iostream.h>
#include<conio.h>
#include<process.h>
class node
{       public:
	int info;
	node* left,*right;
	node* next;

		node()
		{
		    left=0;
		    right=0;
		    next=0;
		}
		node( int a)
		{
			info=a;
			left=0;
			right=0;
			next=0;
		}

};
class queue
{
	node* front,*rear;
		public:
			queue()
			{
			front=0;
			rear=0;
			}
			int isempty();
			void enq(node*);
			node* deq();
};
int queue::isempty()
{
return (front==0);
}
void queue::enq(node* el)
{
	if(!isempty())
	{
		rear->next=el;
		rear=rear->next;
	}
	else
	{
		front=rear=el;
	}
}
node* queue::deq()
{
	if(isempty())
		return 0;
	else
	{
		node* el;
		if(front==rear)
		{
			el=front;
			front=rear=0;
			return el;
		}
		else
		{
			el=front;
			front=front->next;
			return el;
		}
	}
}


class BST
{
	node* root;
	public:
	BST()
	{
		root=0;
	}
	int search(int);
	void insert(int);
	void VLR_preorder(node*);
	void LRV_postorder(node*);
	void LVR_inorder(node*);
	void mirror();
	void level();
	int nonleaf(node*);
	int leaf(node*);
	int height(node*);
	void delbycopy(node* &);
	node* retroot()
	{
		return root;
	}
};
int BST::search(int el)
{
	node* curr=root;
	while(curr!=0)
	{
		if(curr->info==el)
		return 1;
		else if(curr->info<el)
		curr=curr->right;
		else
		curr=curr->left;
	}
	return 0;
}
void BST::insert(int el)
{
	node* curr=root;
	node* p;
	if(curr==0)
	root=new node(el);
	else
	{
		while(curr!=0)
		{
			p=curr;
			if(curr->info<el)
			curr=curr->right;
			else
			curr=curr->left;
		}
		if(p->info<el)
		p->right=new node(el);
		else
		p->left=new node(el);
	}
}
void BST::VLR_preorder(node* curr)
{
	if(curr!=0)
	{
	cout<<curr->info<<" ";
	VLR_preorder(curr->left);
	VLR_preorder(curr->right);
	}
}

void BST::LRV_postorder(node* curr)
{
	if(curr!=0)
	{

	LRV_postorder(curr->left);
	LRV_postorder(curr->right);
	cout<<curr->info<<" ";
	}
}
void BST::LVR_inorder(node* curr)
{
	if(curr!=0)
	{

	LVR_inorder(curr->left);
	cout<<curr->info<<" ";
	LVR_inorder(curr->right);
	}
}

void BST::level()
{
queue q;
node* p=root;
	if(p!=0)
	q.enq(p);
		while(!q.isempty())
		{
			p=q.deq();
			cout<<p->info<<" ";

			if(p->left!=0)
			q.enq(p->left);

			if(p->right!=0)
			q.enq(p->right);
		}
}

void BST::mirror()
{
queue q;
node* p=root;
	if(p!=0)
	q.enq(p);
		while(!q.isempty())
		{
			p=q.deq();
			node* temp=p->left;
			p->left=p->right;
			p->right=temp;

			if(p->left!=0)
			q.enq(p->left);

			if(p->right!=0)
			q.enq(p->right);
		}
}
int BST::nonleaf(node* curr)
{
	int count=0;
	if(curr!=0)
	{
		count+=nonleaf(curr->left);
		if(curr->left!=0&&curr->right!=0)
		count++;
		count+=nonleaf(curr->right);

	}
	return count;
}
int BST::leaf(node* curr)
{
	int count=0;
	if(curr!=0)
	{
		count+=leaf(curr->left);
		if(curr->left==0&&curr->right==0)
		count++;
		count+=leaf(curr->right);

	}
	return count;
}

int BST::height(node* curr)
{
	int l=0,r=0;
	if(curr->left)
	l=height(curr->left);
	if(curr->right)
	r=height(curr->right);
	if(l>r)
	return (l+1);
	else
	return (r+1);
}

void BST::delbycopy(node* &ptr)
{
	node* prev,*temp=ptr;
	if(ptr->right==0)
	ptr=ptr->left;
	else if(ptr->left==0)
	ptr=ptr->right;
	else
	{
		temp=ptr->left;
		prev=ptr;
		while(temp->right!=0)
		{
			prev=temp;
			temp=temp->right;
		}
		ptr->info=temp->info;
		if(prev==ptr)
		prev->left=temp->left;
		else
		prev->right=temp->left;
	}
delete temp;
}
void main()
{
	clrscr();
	BST b;
	int n,c;
	do
	{
		clrscr();
		cout<<"1.insertion"<<"\n";
		cout<<"2.searching"<<"\n";
		cout<<"3.display"<<"\n";
		cout<<"4.pre-order display"<<"\n";
		cout<<"5.post-order display"<<"\n";
		cout<<"6.in-order display"<<"\n";
		cout<<"7.level by display"<<"\n";
		cout<<"8.mirror of tree"<<"\n";
		cout<<"9.non-leaf nodes"<<"\n";
		cout<<"10.leaf nodes"<<"\n";
		cout<<"11.height"<<"\n";
		cout<<"12.delete by copy"<<"\n";
		cout<<"13.Exit"<<"\n";
		cout<<"\n\nenter your choice"<<"\n";
		cin>>c;
		switch(c)
		{
			case 1:cout<<"enter the element to be inserted:"<<"\n";
				cin>>n;
				b.insert(n);
				break;
			case 2:cout<<"enter thr element to be searched:"<<"\n";
				cin>>n;
				cout<<"\n\nPRE_ORDER"<<"\n";
				b.VLR_preorder(b.retroot());
				int t=b.search(n);
				if(t!=0)
				cout<<"\n\nELEMENT FOUND"<<"\n";
				else
				cout<<"\n\nELEMENT NOT PRESENT"<<"\n";
				getch();
				break;
			case 3: cout<<"\n\nPRE_ORDER"<<"\n";
				b.VLR_preorder(b.retroot());
				getch();
				break;
			case 4: cout<<"\n\nPRE_ORDER"<<"\n";
				b.VLR_preorder(b.retroot());
				getch();
				break;
			case 5: cout<<"\n\nPOST-ORDER"<<"\n";
				b.LRV_postorder(b.retroot());
				getch();
				break;
			case 6: cout<<"\n\nIN-ORDER"<<"\n";
				b.LVR_inorder(b.retroot());
				getch();
				break;
			case 7: cout<<"\n\nLEVEL BY LEVEL"<<"\n";
				b.level();
				getch();
			case 8: cout<<"\n\nMIRROR OF TREE"<<"\n";
				b.mirror();
				cout<<"\n\nPRE-ORDER "<<"\n";
				b.VLR_preorder(b.retroot());
				getch();
				break;
			case 9: cout<<"\n\nPRE-ORDER"<<"\n";
				b.VLR_preorder(b.retroot());
				cout<<"\n\nNON LEAF NODES ARE:"<<"\n";
				t=b.nonleaf(b.retroot());
			       cout<<t;
			       getch();
			       break;
			case 10: cout<<"\n\nPRE-ORDER"<<"\n";
				b.VLR_preorder(b.retroot());
				cout<<"\n\nLEAF NODES ARE:"<<"\n";
				t=b.leaf(b.retroot());
			       cout<<t;
			       getch();
			       break;
			case 11: cout<<"\n\nPRE-ORDER"<<"\n";
				b.VLR_preorder(b.retroot());
				cout<<"\n\nHEIGHT OF TREE:"<<"\n";
				t=b.height(b.retroot());
			       cout<<t;
			       getch();
			       break;
			case 12: cout<<"\n\nPRE-ORDER"<<"\n";
				b.VLR_preorder(b.retroot());
				b.delbycopy(b.retroot());
				cout<<"\n\nPRE-ORDER"<<"\n";
				b.VLR_preorder(b.retroot());
				getch();
				break;
			case 13: exit(0);
			default:cout<<"invalid key"<<"\n";
		}
}while(c<14);
getch();
}

actually i want to implement the deletion operation for example deletebymerging ,deletebycopying
my function definiton is void deletebycopy(node* &ptr) them can we call this function in void main this program is okay or not