数据结构：二叉树

// c++11 
// 实现了前序 中序 后序遍历以及获取树的节点个数
#include <iostream>
using namespace std

template <typename T>
class BTreeNode
{
public:
	BTreeNode()
	{
		m_pleft = nullptr;
		m_pright = nullptr;
	}

	BTreeNode<T> * m_pleft;
	BTreeNode<T> * m_pright;
	T  m_value;
};


template <typename T>
class BTree
{

protected:
	BTreeNode<T> * m_root;
public:
	BTree()
	{
		m_root = nullptr;
	}
	bool create()
	{
		cout << "前序遍历的方式构建:" << endl;
		return (m_root = createImp()) ? true : false;
	}
	BTreeNode<T> *  createImp()
	{
		BTreeNode<T>  *p;
		T  ch;
		cin >> ch;
	/*	cout << ch << endl;*/
		if (ch == 0)     //如果到了叶子节点，接下来的左、右子树分别赋值为0
		{
			p = nullptr;
		}
		else
		{
			p = new BTreeNode<T>;
			p->m_value =  ch;
			p->m_pleft = createImp();  //递归创建左子树
			p->m_pright = createImp();  //递归创建右子树
		}
		return p;
	}
	bool empty()
	{
		return (m_root == nullptr) ? true : false;
	}

	int  nodeNum ()const
	{
		return  nodeNumImp(m_root);
	}
	int depth() const
	{
		return depthImp(m_root);
	}

	void  traverse(int flag)  // flag 0  1 2 3 
	{
		if (empty())
		{
			throw  runtime_error("empty tree");
		}
		switch (flag)
		{
			case(0):
				cout << "前序遍历结果:" << endl;
				preOrderTraverseImp(m_root);
				cout << endl;
				break;
			case(1):
				cout << "中序遍历结果:" << endl;
				inOrderTraverseImp(m_root);
				cout << endl;
				break;
			case(2):
				cout << "后序遍历结果:" << endl;
				postOrderTraverseImp(m_root);
				cout << endl;
				break;
			case(3):
				cout << "层次遍历结果:" << endl;
				levelOrderTraverseImp();
				cout << endl;
				break;
			default:
				cout << "Usage: 0 前序  1 中序  2 后序  3 层次" << endl;
				break;
		}

	}

private:
	void  preOrderTraverseImp(BTreeNode<T> * root)
	{
		if (root)
		{
			cout << root->m_value << "	";
			preOrderTraverseImp(root -> m_pleft);
			preOrderTraverseImp(root->  m_pright);
		}

	}

	void  preOrderTraverseImp2(BTreeNode<T> * root)
	{
		// 非递归形式的遍历，利用一个栈，先放右节点，再放左节点
		stack<BTreeNode<T> *> s;
		s.push(m_root);
		while (!s.empty())
		{
			BTreeNode<T> * temp = s.top();
			cout << temp->m_value << "	";
			s.pop();
			if (temp->m_pright)
			{
				s.push(temp->m_pright);
			}
			if (temp->m_pleft)
			{
				s.push(temp->m_pleft);
			}

		}

	}

	void  inOrderTraverseImp(BTreeNode<T> * root)
	{
		if (root)
		{
			inOrderTraverseImp(root->m_pleft);
			cout << root->m_value << "	";
			inOrderTraverseImp(root->m_pright);
		}
	}

	void  inOrderTraverseImp2(BTreeNode<T> * root)
	{
		// 非递归形式
		stack<BTreeNode<T> *> s;
		s.push(m_root);
	
		BTreeNode<T> * temp = s.top();
		while (temp && !s.empty())
		{
			if (temp->m_pleft)
			{
				s.push(temp->m_pleft);
				temp = temp->m_pleft;
			}
			else
			{
				temp = s.top();
				cout << temp->m_value << "	";
				temp = temp->m_right;
				
			}
		}
		while (temp)
		{
			while (temp->left)
			{	
				s.push(temp->left);
				temp = temp->m_pleft;
			}
			cout << temp->m_value << "	";
			temp = s.top();

		}
		
		
		temp = s.top();
		while (temp->m_pright)
		{
			s.push(temp->m_pright);
		}

	
			

		if (temp->m_pright)
		{
			s.push(temp->m_pright);
		}

	

		

	
	
	}

	void  postOrderTraverseImp(BTreeNode<T> * root)
	{
		if (root)
		{
			postOrderTraverseImp(root->m_pleft);
			postOrderTraverseImp(root->m_pright);
			cout << root->m_value << "	";
		}
	}
	void  levelOrderTraverseImp()
	{
		queue<BTreeNode<T>*>   q;
		q.push(m_root);
		while (!q.empty())
		{
			int len = q.size();
			//int depth = 0;
			//cout << "第" << depth << "层" << endl;
			while (len--)
			{
				BTreeNode<T>* temp = q.front();		
				cout << temp->m_value << "	";
				q.pop();
				if (temp->m_pleft)
					q.push(temp->m_pleft);
				if (temp->m_pright)
					q.push(temp->m_pright);

			}
			
		}

	}

	int nodeNumImp(BTreeNode<T> * root)  const
	{
		return (root == nullptr) ? 0 : ( 1 + nodeNumImp(root->m_pleft) +  nodeNumImp(root->m_pright) );
	}
	int depthImp(BTreeNode<T> * root) const
	{
		if (root == NULL)
			return 0;
		
		return (depthImp(root->m_pleft) >depthImp(root->m_pright)  ? \
			depthImp(root->m_pleft) : depthImp(root->m_pright)) + 1 ;
	}


};


int main()
{
	BTree<int>  tree;
	tree.create() ? cout << "创建成功...\n" : cout << "创建失败...\n";
	for (auto i = 0; i < 4; ++i)
	{
		tree.traverse(i);
	}
	cout << endl;
	cout << tree.nodeNum() << endl;
	cout << tree.depth() << endl;
	retrun 0;
}