数据结构——中序线索化二叉树

#include <iostream>
using namespace std;
typedef enum PointerTag {Link,Thread};    //Link==0,Thread==1;线索
typedef struct treenode
{
    struct treenode *left;
    char            data;
    struct treenode *right;
    PointerTag        Ltag,Rtag;    //左右标志
}Treenode,* Treep;
Treep pre;                   /*全局变量，用于二叉树的线索化*/ 
//初始化二叉树
void init_tree(Treep &root)
{
    root=NULL;
    cout<<"初始化成功!"<<endl;
}
//创建二叉树
void creat_tree(Treep &rt)
{
    char ch;
    ch=getchar();
    if('#'==ch)
        rt=NULL;
    else
    {
        rt=(Treep )malloc(sizeof(Treenode));
        rt->data=ch;
        rt->Ltag=Link;
        rt->Rtag=Link;
        creat_tree(rt->left);        //构造左子树
        creat_tree(rt->right);    //构造右子树    
    }
}
//前序遍历二叉树
void pre_order(Treep &rt)
{
    if(rt!=NULL)
    {
        cout<<rt->data<<"  ";
        pre_order(rt->left);
        pre_order(rt->right);
    }
}

//中序线索化二叉树
void InThreading(Treep &p)
{
    if(p)
    {
        InThreading(p->left);
        if(!p->left)
        {
            p->Ltag=Thread;
            p->left=pre;        //前继线索
        }
        if(!pre->right)
        {
            pre->Rtag=Thread;
            pre->right=p;        //后继线索
        }
        pre=p;
        InThreading(p->right);
    }
}//InThreading
Treep InorderThreading(Treep &rt)
{
    Treep thrt;
    if(    !(thrt = (Treep) malloc (sizeof(Treenode) ) ) )
        exit(1);
    thrt->Ltag=Link;
    thrt->Rtag=Thread;    //建头结点
    thrt->right=thrt;    //右指针回指
    if(!rt)
        thrt->left=thrt;    //若二叉树空，则左指针回指
    else
    {
        thrt->left=rt;
        pre=thrt;
        InThreading(rt);        //中序遍历进行中序线索化
        pre->right=thrt;
        pre->Rtag=Thread;
        thrt->right=pre;
    }
    return thrt;
}


//中序遍历线索二叉树
void InorderTraver(Treep &thrt)
{
    Treep p;
    p=thrt->left;
    while(p!=thrt)
    {
        while(p->Ltag==Link)
            p=p->left;
        cout<<p->data<<"  ";
        while(p->Rtag==Thread && p->right!=thrt)
        { 
            p=p->right;
            cout<<p->data<<"  ";
        }
        p=p->right;
    }
}

int main()
{
    Treep root;
    init_tree(root);        //初始化树
    cout<<"请输入二叉树,空值以#代表，输完要以Ctrl+Z表示结束，否则影响下个树的创建!:"<<endl;
    creat_tree(root);        //创建二叉树

    //前序遍历二叉树
    cout<<"前序遍历序列是:"<<endl;
    pre_order(root);
    cout<<endl;

    Treep thrt;
    thrt=InorderThreading(root);
    InorderTraver(thrt);
    cout<<endl;
    return 0;
}