szjy_6_树_044

阅读代码，程序输出是（ ）。

#include <iostream>
using namespace std;

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

void printLeaf(Node* root) {
if (root == nullptr) return;
if (root->left == nullptr && root->right == nullptr) {
cout << root->value << ' ';
return;
}
printLeaf(root->left);
printLeaf(root->right);
}

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.left = &f;
printLeaf(&a);
}

{{ select(1) }}

• 1 2 3
• 2 3 4 5 6
• 6 5 4
• 4 5 6