struct ThreadNode{    int data;    ThreadNode *lchild, *rchild;    int ltag, rtag;};void InThread(ThreadNode *p, ThreadNode *pre){    if(p != NULL){        InThread(p->lchild, pre);        if(p->lchild == NULL){            p->lchild = pre;            p->ltag = 1;        }        if(pre != NULL && pre->rchild == NULL){            pre->rchild = p;            pre->rtag = 1;        }        pre = p;        InThread(p->rchild, pre);    }}void CreateInThread(ThreadNode *T){    ThreadNode *pre = NULL;    if(T != NULL){        InThread(T, pre);        pre->rchild = NULL;        pre->rtag = 1;    }}void InPre(ThreadNode *T, ThreadNode* pre){    if(T->ltag == 1) pre = T->lchild;    else{        ThreadNode* p;        for(p = T->lchild; p->rtag == 0; p = p->rchild);        pre = p;    }}void InNext(ThreadNode *T, ThreadNode* next){    if(T->rtag == 1) next = T->rchild;    else{        ThreadNode* p;        for(p = T->rchild; p->ltag == 0; p = p->lchild);        next = p;    }}