Submission #442794

#	Time	Username	Problem	Language	Result	Execution time	Memory
442794		palilo	Network (BOI15_net)	C++17	0 / 100	1 ms	308 KiB

net

#include <bits/stdc++.h>
using namespace std;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
#ifdef palilo
    freopen("in", "r", stdin);
    freopen("out", "w", stdout);
#endif
    int n;
    cin >> n;
    vector<int> deg(n);
    for (int u, v, i = n - 1; i--;) {
        cin >> u >> v, --u, --v;
        ++deg[u], ++deg[v];
    }
    vector<int> ans;
    for (int i = 0; i < n; ++i) {
        if (deg[i] == 1) {
            ans.emplace_back(i);
        }
    }
    const int leaves = count(deg.begin(), deg.end(), 1);
    cout << (leaves + 1) / 2 << '\n';
    int prv = leaves & 1
                  ? int(find_if(deg.begin(), deg.end(), [&](const auto& x) { return x != 1; }) - deg.begin())
                  : -1;
    for (int i = 0; i < n; ++i) {
        if (deg[i] == 1) {
            if (prv == -1) {
                prv = i;
            } else {
                cout << prv + 1 << ' ' << i + 1 << '\n';
                prv = -1;
            }
        }
    }
}

• Subtask 1: 0 / 18
• Subtask 2: 0 / 45
• Subtask 3: 0 / 37