线索二叉树小例

二叉树在c语言中的重要性不需再说，而线索二叉树则是二叉树中比较重要的一个应用。
一般的二叉树存储模式，空链的数目非常多，线索二叉树则利用这些空链使其指向节点的前驱和后继，改善二叉树的遍历效率。这些被重新利用的空链也就是“线索”了。

中序遍历线索二叉树：

#include <stdio.h>#include <stdlib.h>#define FALSE 0 /* point is not thread */#define TRUE 1 /* point is thread */typedef struct threaded_tree *threaded_pointer;typedef struct threaded_tree{    short int left_thread;    threaded_pointer left_child;    char data;    threaded_pointer right_child;    short int right_thread;}threaded_tree;threaded_pointer pre;threaded_pointer createTp(threaded_pointer T){/* create a binarytree */    char ch;    scanf("%c", &ch);    if(ch == '#')        return NULL;    T = (threaded_pointer)malloc(sizeof(threaded_tree));    T->data = ch;    T->left_thread = FALSE;    T->right_thread = FALSE;    T->left_child = createTp(T->left_child);    T->right_child = createTp(T->right_child);    return T;}void inorderthread(threaded_pointer *p, threaded_pointer T){/* add a root node to tree and thread tree */    (*p) = (threaded_pointer)malloc(sizeof(threaded_tree));    (*p)->left_thread = FALSE;    (*p)->right_thread = FALSE;    (*p)->right_child = (*p);    if(!T){        (*p)->left_child = p;    }    else{        (*p)->left_child = T;        pre = (*p);        in_thread(T);        pre->right_thread = TRUE;        pre->right_child = (*p);    }}void in_thread(threaded_pointer T){/* inorder thread tree */    if(T){        in_thread(T->left_child);        if(!T->left_child){            T->left_thread = TRUE;            T->left_child = pre;        }        if(!pre->right_child){            pre->right_thread = TRUE;            pre->right_child = T;        }        pre = T;        in_thread(T->right_child);    }}/* these two functions can be finded in the book : fundamentals of data structures in C */threaded_pointer insucc(threaded_pointer tree){/* find the inorder sucessor of tree in a threaded binary tree */    threaded_pointer temp;    temp = tree->right_child;    if(!tree->right_thread)        while(!temp->left_thread)            temp = temp->left_child;    return temp;}void tinorder(threaded_pointer tree){/* traverse the threaded binary tree inorder */    threaded_pointer temp = tree;    for(;;){        temp = insucc(temp);        if(temp == tree)            break;        printf("%3c", temp->data);    }    printf("\n");}int main(){    threaded_pointer p, threadTree;    printf("input the binary tree (# == NULL):");    threadTree = createTp(threadTree);    inorderthread(&p, threadTree);    printf("the threaded binary tree: ");    tinorder(p);    return 0;}

程序结果：