二叉树线索化

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#pragma onceenum PointerTag { THREAD, LINK };template <class T>struct BinaryTreeNodeThd{T _data;                         // 数据BinaryTreeNodeThd<T >* _left;  // 左孩子BinaryTreeNodeThd<T >* _right;  // 右孩子PointerTag   _leftTag;            // 左孩子线索标志PointerTag   _rightTag;           // 右孩子线索标志BinaryTreeNodeThd(const T& x):_data(x), _left(NULL), _right(NULL), _leftTag(LINK), _rightTag(LINK){}};template<class T>class BinaryTreeThd{typedef BinaryTreeNodeThd<T> Node;public:BinaryTreeThd(const T* a, size_t size, const T& invalid){size_t index = 0;_root = _CreateTree(a, size, index, invalid);}void InOrderThreading(){Node* prev = NULL;_InOrderThreading(_root, prev);}void PrevOrderThreading(){Node* prev = NULL;_PrevOrderThreading(_root, prev);}void PostOrderThreading();void InOrderThd()//中序线索化打印{Node* cur = _root;while (cur){//1.找最左节点while (cur->_leftTag == LINK)//Link-连接类型{cur = cur->_left;}cout << cur->_data << " ";// 访问连续的后继while (cur->_rightTag == THREAD){cur = cur->_right;cout << cur->_data << " ";}// 访问右子树cur = cur->_right;}cout << endl;}//void PrevOrderThd()//{//Node* cur = _root;//while(cur)//{//while (cur->_leftTag == LINK)//{//cout<<cur->_data<<" ";//cur = cur->_left;//}//cout<<cur->_data<<" ";///*while(cur->_rightTag == THREAD)//{//cur = cur->_right;//cout<<cur->_data<<" ";//}//cur = cur->_right;*///cur = cur->_right;//}//cout<<endl;//}void PrevOrderThd(){Node* cur = _root;while (cur){cout << cur->_data << " ";if (cur->_leftTag == LINK){cur = cur->_left;}else{cur = cur->_right;}}cout << endl;}protected://中序线索化void _InOrderThreading(Node* cur, Node*& prev){if (cur == NULL)return;_InOrderThreading(cur->_left, prev);//先递归到最左if (cur->_left == NULL)//如果左为空，则将cur的左的标志改变{cur->_leftTag = THREAD;//cur->_left = prev;//左边变为prev，因为是中序遍历，左根右}//第一次线索化prev不存在为空，不进入if (prev && prev->_right == NULL){prev->_rightTag = THREAD;//第一次为prev为3prev->_right = cur;//3的右指向2}prev = cur;//将cur变为prev，所以变成每次递归后前一个的数据变为prev//左边线索化完后，递归线索化右_InOrderThreading(cur->_right, prev);}void _PrevOrderThreading(Node* cur, Node*& 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);}}Node* _CreateTree(const T* a, size_t size,size_t& index, const T& invalid){Node* root = NULL;if (index < size && a[index] != invalid){root = new Node(a[index]);root->_left = _CreateTree(a, size, ++index, invalid);root->_right = _CreateTree(a, size, ++index, invalid);}return root;}protected:Node* _root;};void TestThd(){int a1[10] = { 1, 2, 3, '#', '#', 4, '#', '#', 5, 6 };int a2[15] = { 1, 2, '#', 3, '#', '#', 4, 5, '#', 6, '#', 7, '#', '#', 8 };BinaryTreeThd<int> t1(a1, 10, '#');t1.InOrderThreading();t1.InOrderThd();/*t1.PrevOrderThreading();t1.PrevOrderThd();*/BinaryTreeThd<int> t2(a2, 15, '#');//t2.InOrderThreading();//t2.InOrderThd();t2.PrevOrderThreading();t2.PrevOrderThd();}
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