听了国嵌唐老师的课，用C语言实现：

数据结构：线索化二叉树_#include


数据结构：线索化二叉树_i++_02


数据结构：线索化二叉树_#include_03


数据结构：线索化二叉树_#include_04

数据结构：线索化二叉树_i++_05

main.c

#include <stdio.h>
#include <stdlib.h>
#include "BTree.h"
#include "SeqList.h"
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

struct Node
{
    BTreeNode header;
    char v;
};

void print_data(BTreeNode* node)
{
    if(node!=NULL)
    {
        printf("%c",((struct Node*)node)->v);
    }
}

void thread_via_left(BTreeNode* root,BTreeNode** pp)//先序遍历 
{
    if((root!=NULL)&&(pp!=NULL))
    {
        if(*pp!=NULL)
        {
            (*pp)->left = root;
            *pp = NULL;
        }
        
        if(root->left==NULL)
        {
            *pp=root;
        }
        
        thread_via_left(root->left,pp);
        thread_via_left(root->right,pp);
    }
}

void thread_via_list(BTreeNode* root, SeqList* list)
{
    if( (root != NULL) && (list != NULL) )
    {
        SeqList_Insert(list, (SeqListNode*)root, SeqList_Length(list));
        
        thread_via_list(root->left, list);
        thread_via_list(root->right, list);
    }
}

int main(int argc, char *argv[])
{
    BTree* tree = BTree_Create();
    BTreeNode* current = NULL;
    BTreeNode* p = NULL;
    int i = 0;
    SeqList* list = 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'};
    
    BTree_Insert(tree, (BTreeNode*)&n1, 0, 0, 0);
    BTree_Insert(tree, (BTreeNode*)&n2, 0x00, 1, 0);
    BTree_Insert(tree, (BTreeNode*)&n3, 0x01, 1, 0);
    BTree_Insert(tree, (BTreeNode*)&n4, 0x00, 2, 0);
    BTree_Insert(tree, (BTreeNode*)&n5, 0x02, 2, 0);
    BTree_Insert(tree, (BTreeNode*)&n6, 0x02, 3, 0);
    
    printf("Full Tree\n");
    
    BTree_Display(tree,print_data,4,'-');
    
    
    printf("Thread via list:\n");
    
    list = SeqList_Create(BTree_Count(tree));
    
    thread_via_list(BTree_Root(tree),list);

    for(i=0;i<SeqList_Length(list);i++)
    {
        printf("%c, ",((struct Node*)SeqList_Get(list,i))->v);
    }
    
    printf("\n");
    
    
    printf("Thread via left:\n");
    
    current = BTree_Root(tree);
    
    thread_via_left(current,&p);
    
    while(current!=NULL)
    {
        printf("%c, ",((struct Node*)current)->v);
        
        current = current->left;
    }
    
    printf("\n");
    
    BTree_Destroy(tree);
    
    return 0;
}

运行效果：

数据结构：线索化二叉树_i++_06