Submission #727157

#	Time	Username	Problem	Language	Result	Execution time	Memory
727157		cig32	Network (BOI15_net)	C++17	0 / 100	1 ms	324 KiB

net

#include "bits/stdc++.h"
using namespace std;
#define int long long
const int MAXN = 6e5 + 10;
const int MOD = 1e9 + 7;
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
int rnd(int x, int y) {
  int u = uniform_int_distribution<int>(x, y)(rng); return u;
}
int bm(int b, int p) {
  if(p==0) return 1 % MOD;
  int r = bm(b, p >> 1);
  if(p&1) return (((r*r) % MOD) * b) % MOD;
  return (r*r) % MOD;
}
int inv(int b) { 
  return bm(b, MOD-2);
}
int fastlog(int x) {
  return (x == 0 ? -1 : 64 - __builtin_clzll(x) - 1);
}
void printcase(int i) { cout << "Case #" << i << ": "; }
void solve(int tc) {
  int n;
  cin >> n;
  vector<int> adj[n+1];
  for(int i=1; i<n; i++) {
    int u, v;
    cin >> u >> v;
    adj[u].push_back(v);
    adj[v].push_back(u);
  }
  vector<int> v;
  for(int i=1; i<=n; i++) if(adj[i].size() == 1) v.push_back(i);
  cout << (v.size() + 1) / 2 << '\n';
  for(int i=0; i<v.size(); i+=2) {
    cout << v[i] << ' ' << v[(i+1) % (int) v.size()] << '\n';
  }
}
int32_t main() {
  ios::sync_with_stdio(0); cin.tie(0);
  int t = 1; //cin >> t;
  for(int i=1; i<=t; i++) solve(i);
}

Compilation message (stderr)

net.cpp: In function 'void solve(long long int)':
net.cpp:36:17: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |   for(int i=0; i<v.size(); i+=2) {
      |                ~^~~~~~~~~

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