Submission #716597

#	Time	Username	Problem	Language	Result	Execution time	Memory
716597		Spade1	Network (BOI15_net)	C++14	0 / 100	1 ms	324 KiB

net

#pragma GCC optimize("O3")
#include<bits/stdc++.h>
//#include <grader.h>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define ll long long
#define ld long double
#define st first
#define nd second
#define pb push_back
#define INF INT_MAX
#define db double
using namespace std;

const int N = 5e5 + 10;

int cnt[N];

void solve() {
    int n; cin >> n;
    for (int i = 1; i < n; ++i) {
        int u, v; cin >> u >> v;
        cnt[u]++, cnt[v]++;
    }
    vector<int> v;
    for (int i = 1; i <= n; ++i) if (cnt[i]==1) v.pb(i);
    cout << (v.size()+1)/2 << '\n';
    for (int i = 0; i < v.size(); ++i) {
        if (i==v.size()-1) {
            cout << v[i] << " " << v[0] << '\n';
        }
        else {
            cout << v[i] << " " << v[++i] << '\n';
        }
    }
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(NULL);
    int t = 1;
//    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'void solve()':
net.cpp:28:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   28 |     for (int i = 0; i < v.size(); ++i) {
      |                     ~~^~~~~~~~~~
net.cpp:29:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |         if (i==v.size()-1) {
      |             ~^~~~~~~~~~~~
net.cpp:33:38: warning: operation on 'i' may be undefined [-Wsequence-point]
   33 |             cout << v[i] << " " << v[++i] << '\n';
      |                                      ^~~

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