单选题库

TreeNode *searchBST(TreeNode *root, int x) {
    if (root == nullptr || root->val == x)
        return root;
    if (x < root->val)
        return searchBST(root->left, x);
    return   __________________________;
}

void dfs(TreeNode *root) {
    if (root == nullptr)
        return;

    stack<TreeNode *>  s;
    s.push(root);
    while (!s.empty()) {
        TreeNode *node = s.top();
        s.pop();
        cout << node->value << " ";

        ——————————————     // 在此处填入代码
    }
}

s.push(node->right);
s.push(node->left);

s.push(node->left);
s.push(node->right);

if (node->right)
     s.push(node->right);
if (node->left)
     s.push(node->left);

if (node->left)
     s.push(node->left);
if (node->right)
     s.push(node->right);

int height(TreeNode *root) {
    if (root == nullptr)
        return 0;
    int leftH = height(root->left);
    int rightH = height(root->right);
    return   __________________________;
}