二叉树的前中后序遍历（递归与非递归）

/**递归方式遍历**/
//先序递归遍历
void preOrder(Node * root)
{
	if (root != nullptr)
	{
		visit(root);
		preOrder(root->left);
		preOrder(root->right);
	}
}
//中序递归遍历
void inOrder(Node * root)
{
	if (root != nullptr)
	{
		inOrder(root->left);
		visit(root);
		inOrder(root->right);
	}
}
//后序递归遍历
void postOrder(Node * root)
{
	if (root != nullptr)
	{
		postOrder(root->left);
		postOrder(root->right);
		visit(root);
	}
}
/**非递归方式遍历**/
//先序遍历
void preOrderF(Node * root)
{
	if (root == nullptr)
		return;
	stack s;
	s.push(root);
	Node *p = nullptr;
	while (!s.empty())
	{
		p = s.top();
		s.pop();
		cout << p->val << " ";
		if (p->right)
			s.push(p->right);
		if (p->left)
			s.push(p->left);
	}
}
//中序遍历
void inOrderF(Node * root)
{
	if (root == nullptr)
		return;
	stack s;
	Node *p = root;
	while (p||!s.empty())
	{
		if (p)
		{
			s.push(p);
			p = p->left;
		}
		else 
		{
			p = s.top();
			s.pop();
			cout << p->val << " ";
			p = p->right;
		}
	}
	
}
//后序遍历
void postOrderF(Node * root)
{
	if (root == nullptr)
		return;
	stack s;
	vector rs;
	s.push(root);
	Node *p = nullptr;
	while (!s.empty())
	{
		p = s.top();
		s.pop();
		rs.insert(rs.begin(),p->val);
		if (p->left)
			s.push(p->left);
		if (p->right)
			s.push(p->right);
	}
	for (int i = 0; i < rs.size(); i++)
		cout << rs[i] << " ";
}