Fragile network

input/code.cpp: In function 'int main()':
input/code.cpp:17:15: warning: unused variable 'a' [-Wunused-variable]
   17 |     for (auto a : number_edges) {
      |               ^

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    int n;
    std::cin >> n;

    std::vector<int> number_edges(n);
    for (int i = 1; i < n; ++i) {
        int a, b;
        std::cin >> a >> b;
        number_edges[a-1]++;
        number_edges[b-1]++;
    }

    for (auto a : number_edges) {
        //  std::cout << a << " ";
    }

    int count = std::count(number_edges.begin(), number_edges.end(), 1);
    std::cout << count-1 << std::endl;
    auto old_leaf = std::find(number_edges.begin(), number_edges.end(), 1);
    while (old_leaf != number_edges.end()) {
        auto new_leaf = std::find(old_leaf+1, number_edges.end(), 1);
        if (new_leaf == number_edges.end()) return 0;
        std::cout << (old_leaf - number_edges.begin())+1 << " " << (new_leaf - number_edges.begin())+1 << std::endl;
        old_leaf = new_leaf;
    }
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: ACCEPTED

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: ACCEPTED

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: WRONG ANSWER

Test 15

Verdict: WRONG ANSWER

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: WRONG ANSWER

Test 18

Verdict: WRONG ANSWER

Test 19

Verdict: WRONG ANSWER

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: WRONG ANSWER