C++二叉树（类）

 二叉树（建立用的是返回值类型  ，前序、中序、后序 递归遍历） 

#include<iostream>
#include<stack>
using namespace std;
template <class T>
struct root
{
	T val;
	root<T> *left;
	root<T>* right;
};
template <class T>
class BiTree
{
public:
	BiTree() { r = NULL; }
	~BiTree() { clear(r);  }
	void  Build() { r = BuildTree(); }//建树
	void PreOrder() { PreOrder(r); }//前序
	void PreOrder1();  //非递归前序
	void InOrder() { InOrder(r); }//中序
	void EndOrder() { EndOrder(r); }//后序
	void clear() { clear(r); r = NULL;}//清空
private:
	root<T>* BuildTree();
	void clear(root<T>* &r1);
	void PreOrder(root<T>* r);
	void InOrder(root<T>* r);
	void EndOrder(root<T>* r);
	root<T>* r;
};
template<class T>
void BiTree<T>::clear(root<T>* &r1)
{
	if (!r1) return;
	clear(r1->left);
	clear(r1->right);
	delete r1;
}

template <class T>
root<T> * BiTree<T>::BuildTree()
{
	root<T>* k;
	char c;
	cin >> c;
	if (c == '#') return NULL;
	k = new root<T>;
	k->val = c;
	k->left = BuildTree();
	k->right = BuildTree();
	return k;
}
template<class T>
void BiTree<T>::PreOrder(root<T>* r)
{
	if (!r) return;
	cout << r->val << " ";
	PreOrder(r->left);
	PreOrder(r->right);
}
template<class T>
void BiTree<T>::PreOrder1()
{
	if (r == NULL) return;
	stack<root<T>*> s;
	root<T>* t = r;
	while (t || !s.empty())
	{
		while(t)
		{	
			cout << t->val << " ";
			s.push(t);
			t = t->left;
		}
		if (!s.empty())
		{
			t = s.top();	
			s.pop();
			t = t->right;
		}
	}	
}
template<class T>
void BiTree<T>::InOrder(root<T>* r)
{
	if (!r) return;
	InOrder(r->left);
	cout << r->val << " ";
	InOrder(r->right);
}
template<class T>
void BiTree<T>::EndOrder(root<T>* r)
{
	if (!r) return;
	EndOrder(r->left);
	EndOrder(r->right);
	cout << r->val << " ";
}
int main()
{
	BiTree<char> r;
	r.Build();
	r.PreOrder();
	cout << endl;
	r.PreOrder1();
	cout << endl;
	//r.InOrder();
	//cout << endl;
	//r.EndOrder();
	//cout << endl;
	//abc##d##e##
	return 0;
}