线索二叉树

/*线索二叉树运行环境：vs2010*/#include <stdio.h>#include <stdlib.h>#include <malloc.h>#include <string.h>#define NIL '#'#define OK 1#define ERROR 0typedef struct thread_bitree_node thrbitree;typedef enum{LINK,//指针THREAD//线索}pointer_tag;struct thread_bitree_node{char elem;thrbitree *lchild;thrbitree *rchild;pointer_tag ltag;pointer_tag rtag;};/* 功能：先序创建二叉树 返回：创建的节点地址 */  thrbitree *create_thread_bitree(){  char elem;thrbitree *thrbtn = NULL;fflush(stdin);  //清空输入缓冲流scanf("%c", &elem);if(elem == NIL){return thrbtn;}else{thrbtn = (thrbitree *)malloc(sizeof(thrbitree));thrbtn->elem = elem;thrbtn->lchild = create_thread_bitree();if(thrbtn->lchild){thrbtn->ltag = LINK;}else{thrbtn->ltag = THREAD;}thrbtn->rchild = create_thread_bitree();if(thrbtn->rchild){thrbtn->rtag = LINK;}else{thrbtn->rtag = THREAD;}return thrbtn;}}thrbitree *pre;//全局变量,指向刚刚访问过的结点//进行中序线索化void in_threading(thrbitree *thrbtn){if(thrbtn){in_threading(thrbtn->lchild);//递归线索化左子树if(!thrbtn->lchild)//没有左孩子{thrbtn->ltag = THREAD;thrbtn->lchild = pre;}if(!pre->rchild)//前驱没有右孩子{pre->rtag = THREAD;pre->rchild = thrbtn;}pre = thrbtn;in_threading(thrbtn->rchild);//递归线索化右子树}}//中序遍历二叉树T,并将其中序线索化thrbitree *inorder_threading(thrbitree *thrbtn){thrbitree *head = NULL;head = (thrbitree *)malloc(sizeof(thrbitree));memset(head, 0, sizeof(thrbitree));if(!head){exit(ERROR);}head->ltag = LINK;head->rtag = THREAD;head->rchild = head;if(!thrbtn)//二叉树为空{head->lchild = head;}else{head->lchild = thrbtn;pre = head;in_threading(thrbtn);//最后一个结点线索化pre->rchild = head;pre->rtag = THREAD;head->rchild = pre;}return head;}/*中序遍历二叉树并打印*/int inorder_print_threadbitree(thrbitree *headthbtn, int (*visit)(char)){thrbitree *p = NULL;p = headthbtn->lchild;while(p != headthbtn)//空树或者遍历结束时,p==headthbtn{while(p->ltag == LINK){p = p->lchild;}visit(p->elem);while((p->rtag == THREAD) && (p->rchild != headthbtn)){p = p->rchild;visit(p->elem);}p = p->rchild;}return OK;}/*功能：打印传入的参数值*/int print_elem(char elem){printf("%c ", elem);return OK;}/*测试数据：abd###c##中序遍历：dbac*/int main(){thrbitree *thrbtn = NULL;thrbitree *headthrbtn = NULL;thrbtn = create_thread_bitree();  headthrbtn = inorder_threading(thrbtn);  inorder_print_threadbitree(headthrbtn, print_elem);printf("\n");system("pause");return 0;}