preorder前序遍歷

void Binary_tree::preorder()const {
	stack<Node*> s;
	Node* root = this->_root;
	while (true) {
		while (root != nullptr) {
			s.push(root);
			cout << s.top()->val << " ";
			root = root->lchild;
		}
		if (s.empty())
			break;
		root = s.top()->
 
rchild;
		s.pop();
	}
}

inordered 中序遍歷

void Binary_tree::inorder()const {
	stack<Node*> s;
	Node* root = this->_root;
	while (true) {
		while (root != nullptr) {
			s.push(root);
			root = root->lchild;
		}
		if (s.empty())
			break;
		cout << s.top()->val << " ";
		root =
 
 s.top()->rchild;
		s.pop();
	}
}

postorder後序遍歷

void Binary_tree::postorder() const{
	stack<Node*> s1;
	stack<Node*> s2;
	s1.push(_root);
	while (!s1.empty()) {
		Node* temp = s1.top();
		s1.pop();
		s2.push(temp);
		if (temp->lchild != nullptr) {
			s1.push(temp->lchild)
 
;
		}
		if (temp->rchild != nullptr) {
			s1.push(temp->rchild);
		}
	}
	while (!s2.empty()) {
		cout << s2.top()->val << " ";
		s2.pop();
	}
}