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

typedef struct Tree
{
    int data,Ltag,Rtag;
    struct Tree *LChild,*RChild;
}Tree,*Trees;

void CreateTree(Trees *boot)//创建二叉树，具体操作参考上一篇《树与二叉树》
{
    int ch;
    scanf("%d",&ch);
    if(ch==0)
        *boot=NULL;
    else
    {
        *boot=(Trees)malloc(sizeof(Tree));
        (*boot)->data=ch;
        (*boot)->LChild=(*boot)->RChild=NULL;
        (*boot)->Ltag=(*boot)->Rtag=0;
        CreateTree(&((*boot)->LChild));
        CreateTree(&((*boot)->RChild));
    }
}
//添加线索
void InThread(Trees boot)
{
    Trees pre=NULL;
    if(boot)
    {
        InThread(boot->LChild);   
        if(boot->LChild==NULL)
        {
            boot->Ltag=1;
            boot->LChild=pre;
        }
        if(pre!=NULL&&boot->RChild==NULL)
        {
            pre->RChild=boot;
            pre->Rtag=1;
        }
        pre=boot;
        InThread(boot->RChild);
    }
}
//中序找前驱
Tree *InPre(Trees boot)
{
    Trees pre=NULL,q=NULL;
    if(boot->Ltag==1)
        pre=boot->LChild;
    else
    {
        for(q=boot->LChild;q->Rtag==0;q=q->RChild)
            pre=q;   
    }        
    return pre;
}
//中序找后继
Tree *InNext(Trees boot)
{
    Trees Next=NULL,q=NULL;
    if(boot->Rtag==1)
        Next=boot->RChild;
    else
    {
        for(q=boot->RChild;q->Ltag==0;q=q->LChild)
            Next=q;
    }
    return Next;
}
//中序遍历序线索树上的第一个结点
Tree *InFirst(Trees boot)
{
    Trees p=boot;
    if(!p)
        return NULL;
    while(p->Ltag==0)
        p=p->LChild;
    return p;
}
//中序遍历线索二叉树
void TInOrder(Trees boot)
{
    Trees p;
    p=InFirst(boot);
    while(p)
    {
        printf("%2d",p->data);
        p=InNext(p);
    }
    printf("\n");
}
int main()
{
    Trees boot=NULL;
    printf("创建二叉树，输入零结束:\n");
    CreateTree(&boot);
    InThread(boot);

    Trees temp=NULL;
    temp=InPre(boot);
    printf("中序找到的前驱为：\n",temp->data);

    Trees temp1=InNext(boot);
    printf("中序找到的后继为：\n",temp1->data);
   
    Trees bt=InFirst(boot);
    printf("中序遍历序线索树上的第一个结点为：\n",bt->data);
   
    TInOrder(bt);
   
    free(boot);
    free(temp);
    free(temp1);
    free(bt);
    return 0;
}
创建二叉树时：
    样例输入：1（根结点）2（左子树）0（结束左子树的左孩子输入）0（结束左子树的右孩子）输入...以此类推

给位前辈多多指教啊。