Delete node from BST - iterative

[CSharpque]

Hello
I have write program in c++ which delete node from BST. It work for some level.Mean it wrok well when some nodes are delte but when i delete root node program print garbage value infinite time... Here is my code

void del(int num)
{
	struct list *current,*pre,*target;
	current=root;
	if(current==NULL)
		return;
	while((current->left !=NULL) && (current->right!=NULL))
	{
		if(current->data==num)
			target=current;
		if(num < current->data)
		{
			if(current->left ==NULL)
				break;
			pre=current;
			current=current->left;
		}
		else
		{
			if(current->right==NULL)
				break;
			pre=current;
			current=current->right;
		}
	}
	if(target == NULL)
		return;
	else
	{
		if(pre==NULL)
		{
			free(current);
			root=NULL;
		}
		else
		{
			target->data=current->data;
			if(pre->left==current)
				pre->left=current->right;
			else
				pre->right=current->left;
			free (current);
		}
	}
}

anyone help me! and also tell how can i find leaf node in BST....any idea or algorithm?