Submission #443465

#	Time	Username	Problem	Language	Result	Execution time	Memory
443465		BeanZ	Network (BOI15_net)	C++14	0 / 100	15 ms	23808 KiB

net

// I_Love_LPL 1y0m2d
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
const int N = 1e6 + 5;
long long mod = 1000007;
const int lim = 4e5 + 5;
const int lg = 20;
const int base = 311;
const long double eps = 1e-6;
vector<ll> node[N];
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    if (fopen("tests.inp", "r")){
        freopen("test.inp", "r", stdin);
        freopen("test.out", "w", stdout);
    }
    ll n;
    cin >> n;
    for (int i = 1; i < n; i++){
        ll u, v;
        cin >> u >> v;
        node[u].push_back(v);
        node[v].push_back(u);
    }
    vector<ll> one;
    vector<pair<ll, ll>> ans;
    for (int i = 1; i <= n; i++){
        if (node[i].size() == 1){
            one.push_back(i);
        }
    }
    for (int i = 1; i < one.size(); i += 2){
        ans.push_back({one[i], one[i - 1]});
    }
    if (one.size() & 1) ans.push_back({one[0], one[one.size() - 1]});
    cout << ans.size() << endl;
    for (auto j : ans){
        cout << j.first << " " << j.second << endl;
    }
}
/*
Ans:

Out:
*/

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:35:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   35 |     for (int i = 1; i < one.size(); i += 2){
      |                     ~~^~~~~~~~~~~~
net.cpp:17:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   17 |         freopen("test.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
net.cpp:18:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |         freopen("test.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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