C++二叉树基础：源代码实现与操作方法

#include<iostream>
using namespace std;
#include<assert.h>
class BinTreeNode {                                 //结点类的定义
public:
    BinTreeNode () {leftChild =NULL;rightChild =NULL;}        
    BinTreeNode(int x,BinTreeNode *l=NULL,BinTreeNode *r=NULL)
{data=x;leftChild=l;rightChild=r;}
    ~BinTreeNode () {}                                   //析构函数
    BinTreeNode *leftChild,  *rightChild;  //左、右子女链域
    int data;                                              //数据域
};
class BinaryTree{
          public:BinTreeNode  *root;
  int RefValue;
   //void destroy(BinTreeNode* subTree);
BinaryTree(): root (NULL) {}
BinaryTree (int value) {RefValue=value;root=NULL;}
// ~BinaryTree(){ destroy(root);}
  int IsEmpty () { return (root == NULL) ? true : false; }  
    BinTreeNode  *Parent (BinTreeNode *current )
{ return (root == NULL||root == current)?
      NULL:Parent(root, current ); }  
    BinTreeNode  *LeftChild (BinTreeNode *current )
{ return (current!= NULL)? current->leftChild :NULL; }
    BinTreeNode  *RightChild (BinTreeNode  *current )
{ return (current!=NULL) ? current->rightChild : NULL; } 
BinTreeNode  *GetRoot () const { return root; } 
int Insert(const int& item);
     BinTreeNode *Find(int &item)const;

void CreateBinTree(BinTreeNode* &subTree) ;
BinTreeNode *Parent (BinTreeNode * subTree, BinTreeNode  *current ); 
int Height(BinTreeNode  *subTree); 
int Size(BinTreeNode  *subTree);  
void PreOrder(BinTreeNode *subTree );//前序遍历
void InOrder(BinTreeNode *subTree );//中序遍历                         
void PostOrder(BinTreeNode *subTree );//后序遍历        
void levelOrder(BinTreeNode &subTree);//层序遍历                       
void destroy(BinTreeNode* &subTree); 
  int leafsize(BinTreeNode* &subTree);
};
BinTreeNode *BinaryTree::Parent(BinTreeNode *subTree,  BinTreeNode *current) {
//私有函数: 从结点 subTree 开始, 搜索结点 current 的
//双亲, 若找到则返回双亲结点地址, 否则返回NULL
     if (subTree == NULL) return NULL;
     if (subTree->leftChild ==current || 
                subTree->rightChild == current ) 
          return subTree;//找到, 返回父结点地址
           BinTreeNode *p;
     if ((p=Parent(subTree->leftChild, current))!= NULL)  
          return p;          //递归在左子树中搜索
     else return Parent(subTree->rightChild, current);
           //递归在右子树中搜索
};
/*void BinaryTree::destroy(BinTreeNode* subTree) {
//私有函数: 删除根为subTree的子树
     if (subTree != NULL) {
          destroy(subTree->leftChild);     //删除左子树
        destroy(subTree->rightChild);   //删除右子树
        delete subTree;   //删除根结点