Submission #880805

#	Time	Username	Problem	Language	Result	Execution time	Memory
880805		vjudge1	Love Polygon (BOI18_polygon)	C++17	0 / 100	156 ms	18336 KiB

polygon

/// I'm only brave when I have to be
#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define ppb pop_back
#define fast_io ios::sync_with_stdio(false);cin.tie(NULL);
#define file_io freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);
#define FOR(i,k,n) for(int i = k; i < n; ++ i)
#define debf cout<<"(0-0)\n";
#define all(x) x.begin(), x.end()
#define dec(x) cout << fixed << setprecision(x);
#define pf push_front
#define ppf pop_front
#define dash " ------- "
#define what(x) cerr << #x << " is " << x << endl;
#define eb emplace_back
//#define int short int
#define int long long
#define sz(s) (int) (s.size())
#define fl cout.flush()

using namespace std;

typedef long long ll;
typedef pair <int, int> pii;
typedef pair <int, pii> pip;
typedef pair <pii, int> ppi;
typedef pair <ll, ll> pll;
typedef unsigned long long ull;
typedef long double ld;

template <class T> using max_heap = priority_queue <T, vector <T>, less <T> >;
template <class T> using min_heap = priority_queue <T, vector <T>, greater <T> >;

constexpr int MOD = 1e9 + 7, N = 2e5 + 8, M = 1e5, SQ = 300, INF = 2e18 + 8, LGN = 22, mod = 998244353, P = 131113;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

bool mark[N];
int n, pt, sz, ans;
map <string, int> m;
vector <int> adj[N];

void dfs (int u){
  mark[u] = true;
  ++ sz;
  for (int i : adj[u]){
    if (!mark[i]){
      dfs (i);
    }
  }
  return;
}

int32_t main(){
  fast_io;
  cin >> n;
  if (n & 1){
    cout << -1;
    return 0;
  }
  FOR (i, 0, n){
    string ss, tt;
    cin >> ss >> tt;
    if (m[ss] == 0){
      m[ss] = ++ pt;
    }
    if (m[tt] == 0){
      m[tt] = ++ pt;
    }
    adj[m[ss]].pb(m[tt]);
  }
  for (int i = 0; i < n; ++ i){
    if (!mark[i]){
      dfs (i);
      ans += sz / 2;
      ans += (sz & 1);
      sz = 0;
    }
  }
  cout << ans;
  return 0;
}

// Yesterday is history
// Tomorrow is a mystery
// but today is a gift
// That is why it is called the present

• Subtask 1: 0 / 21
• Subtask 2: 0 / 25
• Subtask 3: 0 / 29
• Subtask 4: 0 / 25