以下代码用于统计二叉树的叶节点数量，请在横线处填入代码。
int countLeafNodes(TreeNode* root) {
if (root == nullptr) return 0;
stack<TreeNode*> s;
s.push(root);
int count = 0;
while (!s.empty()) {
TreeNode* node = s.top();
s.pop();
if (node->left == nullptr && node->right == nullptr) {
count++;
}
if (node->right) s.push(node->right);
____________ // 在此处填入代码
}
return count;
}
- A.
if (node->left) s.push(node->left); - B.
if (node->left) s.pop(node->left); - C.
if (node->left) s.front(node->left); - D.
if (node->left) s.push(node->right);