C + + threaded binary tree

Binary tree is a nonlinear structure, and traversal of binary tree is accomplished by recursive or non-recursive traversal by means of a stack assist. When a binary tree is used as a storage structure, it takes a node to get the left child and the right child of the node, and can not directly get the precursor or successor of any of the nodes ' traversal sequences. In order to save the information needed in the traversal, we use the null pointer in the binary tree to the left and right subtree to hold the node's precursor and subsequent information.

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#include  <iostream>using namespace std;enum PointerTag {THREAD, LINK}; template<class t>struct binarytreenodethd{t _data;                       // Data binarytreenodethd<t>* _left;  //left child binarytreenodethd<t>* _right; // Right child pointertag _lefttag;          //left child clue sign    pointertag _righttag;         //right child clue sign    BINARYTREENODETHD (Const t& data): _data (data), _left (null), _right (null), _lefttag (LINK), _righttag ( LINK) {}};TEMPLATE&LT;CLASS&NBSP;T&GT;CLASS&NBSP;BINARYTREETHD{PUBLIC:BINARYTREETHD (Const T* array,  size_t size, const t& invalid) {size_t index = 0;_root =  _createtree (Array, size, index,&nbsP;invalid);} ~BINARYTREETHD () {_destroytree (_root); _root = null;} Void inorderthreading () {binarytreenodethd<t>* prev = null;_inorderthreading (_root,  prev);} Void preorderthreading () {binarytreenodethd<t>* prev = null;_preorderthreading (_root,  prev);} Void postorderthreading () {binarytreenodethd<t>* prev = null;_postorderthreading (_ Root, prev);} VOID&NBSP;PREORDERTHD () {binarytreenodethd<t>* cur = _root;while  (cur) {while  ( Cur && link == cur->_lefttag) {cout<<cur->_data<< " "; cur  = cur->_left;} cout<<cur->_data<< " "; cur = cur->_right;} Cout<<endl;} VOID&NBSP;INORDERTHD () {binarytreenodethd<t>* cur = _root;while  (cur) {while  (cur  && link == cur->_lefttag) {cur = cur->_left;} Cout<<cur->_data<< " ";while  (Thread == cur->_righttag) {cur = cur->_right;cout< <cur->_data<< " ";} Cur = cur->_right;} Cout<<endl;} Protected:binarytreenodethd<t>* _createtree (const t* array, size_t size,  Size_t& index, const t& invalid) {binarytreenodethd<t>* root =  NULL;if  (index < size && array[index] != invalid) {root  = new BinaryTreeNodeThd<T> (Array[index]); Root->_left = _createtree (Array,  size, ++index, invalid); Root->_right = _createtree (Array, size, ++index ,  invalid);} Return root;} Void _destroytree (Binarytreenodethd<t>* root) {if  (null == root) return;if  ( Link == root->_lefttag) _destroytree (root->_left);if  (Link == root->_righttag ) _destroytree (Root->_right);d Elete root;} Void _preorderthreading (binarytreenodethd<t>* cur, binarytreenodethd<t>*&  prev) {if  (null == cur) return;if  (null == cur->_left) {cur->_leftTag =  thread;cur->_left = prev;} if  (prev && null == prev->_right) {prev->_righttag = thread; Prev->_right = cur;} prev = cur;if  (Cur->_lefttag == link) _preorderthreading (Cur->_left, prev); if  (Cur->_righttag == link) _preorderthreading (Cur->_right, prev);} Void _inorderthreading (binarytreenodethd<t>* cur, binarytreenodethd<t>*&  prev) {if  (null == cur) return;_inorderthreading (Cur->_left, prev);if  (NULL ==  cur->_left) {Cur->_lefttag = thread;cur->_left = prev;} if  (prev && null == p rev->_right) {prev->_righttag = thread;prev->_right = cur;} Prev = cur;_inorderthreading (Cur->_right, prev);} Void _postorderthreading (binarytreenodethd<t>* cur, binarytreenodethd<t>*&  prev) {if  (null == cur) return;_postorderthreading (Cur->_left, prev); _ Postorderthreading (Cur->_right, prev);if  (cur->_left == null) {cur->_leftTag  = thread;cur->_left = prev;} if  (prev && null == prev->_right) {prev->_righttag = thread; Prev->_right = cur;} Prev = cur;} protected:binarytreenodethd<t>* _root;}; Void test () {int a[] = {1, 2, 3,  ' # ',  ' # ', 4,  ' # ',  ' # ',  5, 6}; Binarytreethd<int> t1 (A, sizeof (a)/sizeof (a[0]),  ' # '); t1. Preorderthreading (); T1. PREORDERTHD (); Binarytreethd<int> t2 (A, sizeof (a)/sizeof (a[0]),  ' # '); T2. Inorderthreading (); T2. INORDERTHD ();int a1[] = {1, 2,  ' # ', 3,  ' # ',  ' # ', 4, 5,  ' # ', 6,  ' # ', 7,  ' # ',  ' # ', 8}; Binarytreethd<int> t3 (a1, sizeof (A1)/sizeof (A1[0]),  ' # '); T3. Preorderthreading (); T3. PREORDERTHD ();} Int main () {Test (); return 0;}

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C + + threaded binary tree