线索化二叉树--节点空指针实现过程

方法1：通过节点空指针来实现；

//BTree.h#ifndef _BTREE_H_#define _BTREE_H_#define BT_LEFT 0#define BT_RIGHT 1typedef unsigned long long BTPos;   //64bit typedef void BTree;typedef struct _tag_BTreeNode BTreeNode;     //define the node pointerstruct _tag_BTreeNode{BTreeNode* left;BTreeNode* right;};typedef void (BTree_Printf)(BTreeNode*);BTree* BTree_Create();void BTree_Destroy(BTree* tree);void BTree_Clear(BTree* tree);int BTree_Insert(BTree* tree,BTreeNode* node,BTPos pos,int count,int flag); void BTree_Display(BTree* tree,BTree_Printf* pFunc,int gap,char div);BTreeNode* BTree_Delete(BTree* tree,BTPos pos,int count);BTreeNode* BTree_Get(BTree* tree,BTPos pos,int count);BTreeNode* BTree_Root(BTree* tree);int BTree_Height(BTree* tree);int BTree_Count(BTree* tree);int BTree_Degree(BTree* tree);#endif

//BTree.c#include "BTree.h"#include <malloc.h>#include <stdio.h>typedef struct _tag_TBTree TBTree;struct _tag_TBTree     //define the node of header {int count;BTreeNode* root;};static int recursive_degree(BTreeNode* root){int ret = 0;if(root!=NULL){if(root->left!=NULL){ret++;}if(root->right!=NULL){ret++;}if(ret == 1){int ld = recursive_degree(root->left);int rd = recursive_degree(root->right);if(ret < ld){ret = ld;}if(ret < rd){ret = rd;}}}return ret;}static int recursive_height(BTreeNode* root){int ret = 0;if(root!=NULL){int lh = recursive_height(root->left);int rh = recursive_height(root->right);ret = ((lh>rh)?lh:rh) + 1;}return ret;}static int recursive_count(BTreeNode* node){int ret = 0;if(node!=NULL){ret = recursive_count(node->left) + 1 + recursive_count(node->right);}return ret;}static void recursive_display(BTreeNode* node,BTree_Printf* pFunc,int format,int gap,char div){int i = 0;if((node!=NULL)&&(pFunc!=NULL)){for(i=0;i<format;i++){printf("%c",div);}pFunc(node);printf("\n");if((node->left!=NULL)||(node->right!=NULL)){recursive_display(node->left,pFunc,format+gap,gap,div);recursive_display(node->right,pFunc,format+gap,gap,div);}}else   //when there  has only-left child node or only-right child node,print the char to fill the place{for(i=0;i<format;i++){printf("%c",div);}printf("\n");}}BTree* BTree_Create(){TBTree* ret = (TBTree*)malloc(sizeof(TBTree));if(ret != NULL){ret->count = 0;ret->root = NULL;}return ret;}void BTree_Destroy(BTree* tree){free(tree);}void BTree_Clear(BTree* tree){TBTree* btree = (TBTree*)tree;if(btree != NULL){btree->count = 0;btree->root = NULL;}}int BTree_Insert(BTree* tree,BTreeNode* node,BTPos pos,int count,int flag)   // pos :position; count :moving times;{int ret = 0;int bit = 0;TBTree* btree = (TBTree*)tree;ret = (btree!=NULL)&&(node!=NULL)&&((flag==BT_LEFT)||(flag==BT_RIGHT));if(ret){BTreeNode* parent = NULL;BTreeNode* current = btree->root;node->left = NULL;node->right = NULL;while((count>0)&&(current!=NULL)){bit = pos & 1;pos = pos >> 1;parent = current;if(bit==BT_LEFT){current = current->left;}else if(bit==BT_RIGHT){current = current->right;}count--;}if(flag==BT_LEFT)    //when the current node has some children node,the current node should be inserted after the node{node->left = current;}else if(flag == BT_RIGHT){node->right = current;}if(parent!=NULL){if(bit == BT_LEFT){parent->left = node;}else if(bit == BT_RIGHT){parent->right = node;}}else      //insert the first node{btree->root = node;}btree->count++;}return ret;} void BTree_Display(BTree* tree,BTree_Printf* pFunc,int gap,char div){TBTree* btree = (TBTree*)tree;if((btree!=NULL)&&(pFunc!=NULL)){recursive_display(btree->root,pFunc,0,gap,div);}}BTreeNode* BTree_Delete(BTree* tree,BTPos pos,int count){BTreeNode* ret = NULL;TBTree* btree = (TBTree*)tree;      //×öÒ»¸ö¿Ç int bit = 0;if(btree!=NULL){BTreeNode* parent = NULL;BTreeNode* current = btree->root;while((count>0)&&(current!=NULL)){bit = pos & 1;pos = pos >> 1;parent = current;if(bit==BT_LEFT){current = current->left;}else if(bit==BT_RIGHT){current = current->right;}count--;}if(parent!=NULL){if(bit==BT_LEFT){parent->left = NULL;}else if(bit == BT_RIGHT){parent->right = NULL;}}else   //the only one node{btree->root = NULL;}ret = current;    //importantbtree->count = btree->count - recursive_count(ret);}return ret;}BTreeNode* BTree_Get(BTree* tree,BTPos pos,int count){BTreeNode* ret = NULL;TBTree* btree = (TBTree*)tree;int bit = 0;if(btree!=NULL){BTreeNode* parent = NULL;BTreeNode* current = btree->root;while((count>0)&&(current!=NULL)){bit = pos & 1;pos = pos >> 1;parent = current;      //record the current nodeif(bit == BT_LEFT){current = current->left;}else if(bit == BT_RIGHT){current = current->right;}count--;}ret = current;   //important}return ret;}BTreeNode* BTree_Root(BTree* tree){BTreeNode* ret = NULL;TBTree* btree = (TBTree*)tree;if(btree != NULL){ret = btree->root;}return ret;}int BTree_Height(BTree* tree){int ret = 0;TBTree* btree = (TBTree*)tree;if(btree!=NULL){ret = recursive_height(btree->root);}return ret;}int BTree_Count(BTree* tree){int ret = 0;TBTree* btree = (TBTree*)tree;if(btree!=NULL){ret = btree->count;}return ret;}int BTree_Degree(BTree* tree){int ret = 0;TBTree* btree = (TBTree*)tree;if(btree!=NULL){ret = recursive_degree(btree->root);}return ret;}

//main.c /*-----------time: 2016-4-8version: DEV-C++ 5.2.0.3 -----------*/#include <stdio.h>#include <stdlib.h>#include "BTree.h"struct Node{BTreeNode header;char v;};void print_data(BTreeNode* node){if(node!=NULL){printf("%c",((struct Node*)node)->v);}}void pre_order_traversal(BTreeNode* root){if(root!=NULL){printf("%c,",((struct Node*)root)->v);pre_order_traversal(root->left);pre_order_traversal(root->right);}}void thread_via_left(BTreeNode* root,BTreeNode** pt){if((root!=NULL)&&(pt!=NULL)){if(*pt != NULL){(*pt)->left = root;*pt = NULL;}if(root->left == NULL){*pt = root;}thread_via_left(root->left,pt);thread_via_left(root->right,pt);}}int main(int argc, char *argv[]) {BTree* tree = BTree_Create();BTreeNode* pt = NULL;BTreeNode* current = NULL;struct Node n1 = {{NULL,NULL},'A'};struct Node n2 = {{NULL,NULL},'b'};struct Node n3 = {{NULL,NULL},'C'};struct Node n4 = {{NULL,NULL},'D'};struct Node n5 = {{NULL,NULL},'E'};struct Node n6 = {{NULL,NULL},'F'};struct Node n7 = {{NULL,NULL},'G'};BTree_Insert(tree,(BTreeNode*)&n1,0,0,0);     //ABTree_Insert(tree,(BTreeNode*)&n2,0x00,1,0);  //bBTree_Insert(tree,(BTreeNode*)&n3,0x01,1,0);  //CBTree_Insert(tree,(BTreeNode*)&n4,0x00,2,0);  //DBTree_Insert(tree,(BTreeNode*)&n5,0x02,2,0);  //EBTree_Insert(tree,(BTreeNode*)&n6,0x01,2,0);  //FBTree_Insert(tree,(BTreeNode*)&n7,0x03,2,0);  //FBTree_Display(tree,print_data,2,'-');printf("pre_order_traversal (Ç°Ðò±éÀú): \n");pre_order_traversal(BTree_Root(tree));printf("\n");current = BTree_Root(tree);thread_via_left(current,&pt);if(current!=NULL){printf("thread_via_left: \n");while(current!=NULL){printf("%c,",((struct Node*)current)->v);current = current->left;}}BTree_Destroy(tree);return 0;}

输出：

A
--b
----D
----E
--C
----F
----G
pre_order_traversal (前序遍历):
A,b,D,E,C,F,G,
thread_via_left:
A,b,D,E,C,F,G,


Process exited normally.
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