下列代码实现了树的深度优先遍历，则横线处应填入（ ）。struct TreeNode { int val; TreeNode* left; TreeNode* right; TreeNode(int x): val(x), left(nullptr), right(nullptr) {} }; void dfs(TreeNode* root) { if (!root) return; stack st; st.push(root); while (!st.empty()) { TreeNode* node = st.top(); st.pop(); cout val right) st.push(node->right); ________________________ } }
A. if (node->left) st.push(node->left);Copy
B. if (node->left) st.pop(node->left);Copy
C. if (node->left) st.front(node->left);Copy
D. if (node->left) st.push(node->right);Copy
正确答案：A
试卷来源：202512 CCF-GESP编程能力等级认证C++六级真题