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;
}