线索二叉树

#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cstring>
#include<malloc.h>
using namespace std;

typedef char ElemType; 

//线索存储标志位
//Link(0)表示指向左右孩子的指针
//Thread(1)表示指向前驱后继的线索 
typedef enum {
    Link,Thread
}PointerTag;

typedef struct BiThrNode{
    char data;
    struct BiThrNode *lchild,*rchild;
    PointerTag ltag;
    PointerTag rtag;
}BiThrNode,*BiThrTree;

//全局变零，始终指向刚刚访问过的结点
BiThrTree pre;

//创建一颗二叉树，用户遵照前序遍历输入数据
void CreateBiThrTree(BiThrTree &T){
    char c;
    scanf("%c",&c);
    if(' ' == c)
        T = NULL;
    else{
        T = (BiThrNode *)malloc(sizeof(BiThrNode));
        T->data = c;
        T->ltag = Link;
        T->rtag = Link;
        CreateBiThrTree(T->lchild);
        CreateBiThrTree(T->rchild);
    }
} 

//中序遍历线索化
void InThreading(BiThrTree &T){
    if(T){
        InThreading(T->lchild);//递归左孩子线索化
        if(!T->lchild){//如果该结点没有左孩子，设置ltag为Thread，并把lchid指向上一个刚刚访问的结点 
            T->ltag = Thread;
            T->lchild = pre;
        }
        if(!pre->rchild){
            pre->rtag = Thread;
            pre->rchild = T; 
        } 
        pre = T;
        InThreading(T->rchild);//递归右孩子线索化 
    }
} 

void InOrderThreading(BiThrTree &p,BiThrTree &T){
    p = (BiThrNode *)malloc(sizeof(BiThrNode));
    p->ltag = Link;
    p->rtag = Thread;
    p->rchild = p;
    if(!T)
        p->lchild = p;
    else{
        p->lchild = T;
        pre = p;
        InThreading(T);
        pre->rchild = p;
        pre->rtag = Thread;
        p->rchild = pre;
    }
}

void visit(char c){
    printf("%c",c);
}

//中序遍历，非递归
void InOrderTraverse(BiThrTree T){
    BiThrTree p;
    p = T->lchild;
    while(p!=T){
        while(p->ltag==Link)
            p = p->lchild;
        visit(p->data);
        while(p->rtag==Thread&&p->rchild!=T){
            p = p->rchild;
            visit(p->data);
        }
        p = p->rchild;
    }
} 

int main(){
    BiThrTree p,T = NULL;
    CreateBiThrTree(T);
    InOrderThreading(p,T);
    printf("中序遍历输出结果为：");
    InOrderTraverse(p); 
    printf("
");
    return 0;
}