非递归遍历

void PreOrder(BTNode* b)
{
	BTNode* p;
	BTNode* St[MAXSIZE];
	int top = -1;
	p = b;
	while (p != NULL || top != -1)
	{
		while (p != NULL)
		{
			printf("%c ", p->data);
			St[++top] = p;
			p = p->lchild;
		}
		if (top != -1)
		{
			p = St[top--];
			p = p->rchild;
		}
	}
}

void InOrder(BTNode* b)
{

	BTNode* p;
	BTNode* St[MAXSIZE];
	int top = -1;
	p = b;
	while (p != NULL || top != -1)
	{
		while (p != NULL)
		{
			St[++top] = p;
			p = p->lchild;
		}
		if (top != -1)
		{
			p = St[top--];
			printf("%c", p->data);
			p = p->rchild;
		}
	}
}

void PostOrder(BTNode* b)
{
	BTNode* p, * r;
	BTNode* St[MAXSIZE];
	int top = -1;
	p = b;
	bool flag = true;
	do
	{
		while (p != NULL)
		{
			St[++top] = p;
			p = p->lchild;
		}
		r = NULL;
		flag = true;
		while (flag && top != -1)
		{
			p = St[top];
			if (p->rchild == r)
			{
				printf("%c", p->data);
				top--;
				r = p;
			}
			else
			{
				p = p->rchild;
				flag = false;
			}
		}
	} while (top!=-1);
}

void LevelOrder(BTNode* b)
{
	BTNode* p = b;
	BTNode* qu[MAXSIZE];
	int front = -1;
	int rear = -1;
	qu[++rear] = p;
	while (rear != front)
	{
		p = qu[++front];
		printf("%c", p->data);
		if (p->lchild)
			qu[++rear] = p->lchild;
		if (p->rchild)
			qu[++rear] = p->rchild;
	}
}