szjy_6_树_040

规定根结点位于第 1 层。阅读代码，程序输出是（ ）。

#include <iostream>
using namespace std;

struct Node {
int value;
Node* left = nullptr;
Node* right = nullptr;
};

int countAtLevel(Node* root, int k) {
if (root == nullptr) return 0;
if (k == 1) return 1;
return countAtLevel(root->left, k - 1)
+ countAtLevel(root->right, k - 1);
}

int main() {
Node a{1}, b{2}, c{3}, d{4}, e{5}, f{6};
a.left = &b;  a.right = &c;
b.left = &d;  b.right = &e;
c.right = &f;
cout << countAtLevel(&a, 3);
}

{{ select(1) }}

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