二叉树的线索遍历

#include<iostream>
#include<assert.h>
using namespace std;
enum PointerTag
{
	THREAD,
	LINK
};
template<class T>
struct BinaryTreeNodeThd
{
	T _data;
	BinaryTreeNodeThd<T>* _left;
	BinaryTreeNodeThd<T>* _right;
	BinaryTreeNodeThd<T>* _parent;
	PointerTag _leftTag;
	PointerTag _rightTag;
	BinaryTreeNodeThd(const T& x)
		:_data(x)
		,_left(NULL)
		,_right(NULL)
		,_parent(NULL)
		,_leftTag(LINK)
		,_rightTag(LINK)
	{}
};
template<class T>
class BinaryTreeThd
{
public:
	BinaryTreeThd()
		:_root(NULL)
	{}
	BinaryTreeThd(const T* a,size_t size)
	{
		size_t index=0;
		_root=_CreateTree(a,index,size);
	}
	void InOrderThreading()
	{
		BinaryTreeNodeThd<T>* prev=NULL;
		_InOrderThreading(_root,prev);
	}
	void PrevOrderThreading()
	{
		BinaryTreeNodeThd<T>* prev=NULL;
		_PrevOrderThreading(_root,prev);
	}
	void PostOrderThreading()
	{
		BinaryTreeNodeThd<T>* prev=NULL;
		_PostOrderThreading(_root,prev);
	}
	void InOrderThd()
	{
		BinaryTreeNodeThd<T>* cur=_root;
		while(cur)
		{
			//找最左节点
			while((cur)&&(cur->_leftTag!=THREAD))
			{
				cur=cur->_left;
			}
			cout<<cur->_data<<" ";
			//访后继
			while(cur->_rightTag !=LINK)
			{
				cur=cur->_right;
				cout<<cur->_data<<" ";
			}
			//跳转到右子树
			cur=cur->_right;
		}
		cout<<endl;
	}
	void PrevOrderThd()
	{
		BinaryTreeNodeThd<T>* cur=_root;
		while(cur)
		{
			while(cur&&cur->_leftTag==LINK)
			{
				cout<<cur->_data<<" ";
				cur=cur->_left;
			}
			cout<<cur->_data<<" ";
			cur=cur->_right;
		}
		cout<<endl;
	}
	void PostOrderThd()
	{
		BinaryTreeNodeThd<T>* cur=_root;
		BinaryTreeNodeThd<T>* prev=NULL;
		while(1)
		{
			while(cur&&cur->_leftTag==LINK)
			{
				cur=cur->_left;
			}
			//当子节点为THRED时，遍历左右回到根节点
			while(cur&&cur->_rightTag==THREAD)
			{
				cout<<cur->_data<<" ";
				prev=cur;
				cur=cur->_right;
			}
			if(cur==_root)
			{
				cout<<_root->_data<<" ";
				break;
			}
			//判断右节点有没有访问过
			if(cur&&cur->_leftTag==LINK&&cur->_right==prev)
			{
				cout<<cur->_data<<" ";
				cur=cur->_parent;
			}
			//当子节点为LINK类型，遍历右子树
			if(cur&&cur->_rightTag==LINK)
			{
				cur=cur->_right;
			}
		}
		cout<<endl;
	}
protected:
	BinaryTreeNodeThd<T>* _root;
	BinaryTreeNodeThd<T>* _CreateTree(const T* _array,size_t& index,size_t size)
	{
		BinaryTreeNodeThd<T>* root=NULL;
		if(index<size&&_array[index]!=‘#‘)
		{
			root=new BinaryTreeNodeThd<T>(_array[index]);
			root->_left=_CreateTree(_array,++index,size);
			if (root->_left)
			{
				root->_left->_parent = root;
			}
			root->_right = _CreateTree(_array, ++index, size);
			if (root->_right)
			{
				root->_right->_parent = root;
			}
		}
		return root;
}
	void _InOrderThreading(BinaryTreeNodeThd<T>* cur,BinaryTreeNodeThd<T>*& prev)
	{
		if(cur==NULL)
			return;
		_InOrderThreading(cur->_left,prev);
		if(cur->_left==NULL)
		{
			cur->_leftTag =THREAD;
			cur->_left=prev;
		}
		if(prev&&prev->_right==NULL)
		{
			prev->_rightTag=THREAD;
			prev->_right =cur;
		}
		prev=cur;
		_InOrderThreading(cur->_right,prev);
	}
	void _PrevOrderThreading(BinaryTreeNodeThd<T>* cur,BinaryTreeNodeThd<T>*& prev)
	{
		if(cur==NULL)
			return;
		if(cur->_left==NULL)
		{
			cur->_leftTag=THREAD;
			cur->_left=prev;
		}
		if(prev&&prev->_right==NULL)
		{
			prev->_rightTag=THREAD;
			prev->_right=cur;
		}
		prev=cur;
		if(cur->_leftTag == LINK)
			_PrevOrderThreading(cur->_left,prev);
		if(cur->_rightTag == LINK)
			_PrevOrderThreading(cur->_right,prev);
	}
	void _PostOrderThreading(BinaryTreeNodeThd<T>* cur,BinaryTreeNodeThd<T>*& prev)
	{
		if(cur==NULL)
			return;
		_PostOrderThreading(cur->_left,prev);
		_PostOrderThreading(cur->_right,prev);
		if(cur->_left==NULL)
		{
			cur->_leftTag=THREAD;
			cur->_left=prev;
		}
		if(prev&&prev->_right==NULL)
		{
			prev->_rightTag=THREAD;
			prev->_right=cur;
		}
		prev=cur;
	}
};
void Test1()
{
	//char _array[10]={‘a‘,‘b‘,‘d‘,‘#‘,‘#‘,‘e‘,‘#‘,‘#‘,‘c‘,‘f‘};
	int _array[10] = {1, 2, 3, ‘#‘, ‘#‘, 4, ‘#‘, ‘#‘, 5, 6};
	BinaryTreeThd<int> btt1(_array,10);
	btt1.InOrderThreading();
	btt1.InOrderThd();
	BinaryTreeThd<int> btt2(_array,10);
	btt2.PrevOrderThreading();
	btt2.PrevOrderThd();
	BinaryTreeThd<int> btt3(_array,10);
	btt3.PostOrderThreading();
	btt3.PostOrderThd();
}
int main()
{
	Test1();
	system("pause");
	return 0;
}

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二叉树的线索遍历

原文：http://10707460.blog.51cto.com/10697460/1757511