线索二叉树

TBTNode* pre;
void Thread(TBTNode*& p)
{
	if (p != NULL)
	{
		Thread(p->lchild);
		if (p->lchild == NULL)
		{
			p->lchild = pre;
			p->ltag = 1;
		}
		else
			p->ltag = 0;
		if (pre->rchild == NULL)
		{
			pre->rchild = p;
			pre->rtag = 1;
		}
		else
			pre->rtag = 0;
		pre = p;
		Thread(p->rchild);
	}
}

TBTNode* CreateThread(TBTNode* b)
{
	TBTNode* root;
	root=(TBTNode*)malloc(sizeof(TBTNode));
	root->ltag = 0;
	root->rtag = 1;
	root->rchild = b;
	if (b == NULL)
		root->lchild = root;
	else
	{
		root->lchild = b;
		pre = root;
		Thread(b);
		pre->rtag = 1;
		pre->rchild = root;
		root->rchild = pre;
	}
	return root;
}

void ThInOrder(TBTNode* tb)
{
	TBTNode* p = tb->lchild;
	while (p != tb)
	{
		while (p->ltag == 0)
			p = p->lchild;
		printf("%c", p->data);
		while (p->rtag == 1 && p->rchild != tb)
		{
			p = p->rchild;
			printf("%c", p->data);
		}
		p = p->rchild;
	}
}