二叉树，递归，非递归遍历

struct node
{
	int data;
	node* left;
	node* right;
	int tag = 1;
}
void reNode(node* root)
{
	if(root == NULL)
		return;
	//cout << root->data << endl; //递归前序遍历
	reNode(root->left);
	//cout << root->data << endl; //递归中序遍历
	reNode(root->right);
	//cout << root->data << endl; //递归后序遍历
}
void teNode(node* root)
{
        node* p = root;
        stack<node*> s;
        while(p != NULL || !s.empty())
        {
                while(p != NULL)
                {
                        s.push_back(p);
                        //cout << p->data << endl; //前序遍历
                        p = p->left;
                }
                if(!s.empty())
                {
                        p = s.top();
                        s.pop();
                        //cout << p->data << endl; // 中序遍历
                        p = p->right();
                }
        }
}
void posNode(node* root)
{
	stack<node*> s;
	node* p = root;
	while(p != NULL || !s.empty())
	{
		while(!p)
		{
			s.push_back(p);
			p = p->left;
		}
		if(!s.empty())
		{
			p = s.top();
			if(p->tag)
			{
				cout << p->data << endl; // 后序遍历
				s.pop();
				p = NULL;
			}
			else
			{
				p->tag = 1;
				p = p->right;
			}
		}
	}
}