二叉树的创建与遍历

 

#include <stdio.h>
#include <stdlib.h>

typedef enum {Link, Thread} PointerTag;

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

BiThrTree pre;

//前序遍历 输入
CreateBiThrTree (BiThrTree *T)         // 双重指针  (*T)指向二叉树节点    T 指向*T的位置；
{
    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);      //双重指针
        CreateBiThrTree (&(*T)->rchild);
    }
}

//中序遍历线索
InThreading (BiThrTree T)
{
    if (T)
    {
        InThreading (T->lchild);     //递归左孩子线索化
        if (!T->lchild)            //如果该节点没有左孩子， 设置ltag 为thread，并把lchild指向前驱
        {
            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
    }
}

InOrderThreading (BiThrTree *p, BiThrTree T)
{
    *p =(BiThrTree) 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;
    }
}

int main()
{
    BiThrTree P, T = NULL;        //指针T指向NULL

    CreateBiThrTree (&T);         //指针T的地址 传入。。

    InOrderThreading (&P, T);
}