Tietoverkko

#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define IO ios_base::sync_with_stdio(0); cin.tie(0)
#define ff first
#define ss second
#define pb push_back
#define INF 2147483647
#define LINF (1LL<<62LL)
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

int n;
vector<int> adj[101010];
bool V[101010];
int val[101010];

void dfs(int x, int v, int p) {
  if (V[x]) {
    // backtrace
    cout<<n-(v-val[x])<<"\n";
    exit(0);
  }
  
  V[x] = true;
  val[x] = v;
  for (int u : adj[x]) {
    if (u != p) dfs(u, v+1, x);
  }
}

int main() {
  IO; cin>>n;
  FOR(i,0,n) {
    int a,b; cin>>a>>b;
    adj[a].pb(b);
    adj[b].pb(a);
  }
  
  dfs(1,0,1);
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED