前序遍历

void preOrder(Node *node){if(node != nullptr){cout << node->data_ << " ";preOrder(node->left_);preOrder(node->right_);}}

中序遍历

void inOrder(Node *node){if (node != nullptr){inOrder(node->left_);cout << node->data_ << " ";inOrder(node->right_);}}

后序遍历

void postOrder(Node *node){if (node != nullptr){postOrder(node->left_);postOrder(node->right_);cout << node->data_ << " ";}}

层序遍历

递归实现求二叉树的层数，求以node为根节点的子树的高度

int level(Node* node){if(node == nullptr){return 0;}int left = level(node->left_);int right = level(node->right_);return left > right ? left + 1 : right + 1;}

递归求二叉树节点的个数

int number(Node *node){if(node == nullptr){return 0;}int left = number(node->left_);int right = number(node->right_);return left + right + 1;}

// 递归层数遍历void levelOrder(){int h = level();for(int i = 0; i < h; i++){levelOrder(root_, i);}}void levelOrder(Node *node, int i){if(node == nullptr){return;}if(i == 0){cout << node->data_ << " ";return;}levelOrder(node->left_, i - 1);levelOrder(node->right_, i - 1);}