Submission #880814

#	Time	Username	Problem	Language	Result	Execution time	Memory
880814		vjudge1	Love Polygon (BOI18_polygon)	C++17	46 / 100	707 ms	21592 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 = 21, mod = 998244353, P = 131113;

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

bool mark[N];
int n, pt, sz, ans, mat[25][25], dp[(1<<LGN)];
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;
  }
  if (n <= 20){
    set <string> s;
    FOR (i, 0, n){
      string ss, tt;
      cin >> ss >> tt;
      if (s.find(ss) == s.end()){
        m[ss] = pt ++;
        s.insert(ss);
      }
      if (s.find(tt) == s.end()){
        m[tt] = pt ++;
        s.insert(tt);
      }
      mat[m[ss]][m[tt]] = 1;
      //cout << m[ss] << " " << m[tt] << '\n';
    }
    fill (dp, dp + (1 << LGN), INF);
    dp[0] = 0;
    for (int i = 1; i < (1 << n); ++ i){
      for (int j = 0; j < n; ++ j){
        if (i & (1 << j)){
          for (int k = 0; k < n; ++ k){
            if ((i & (1 << k)) && j != k){
              dp[i] = min (dp[i], dp[i^(1<<j)^(1<<k)] + 2 - mat[j][k] - mat[k][j]);
              //cout << i << " updated from " << (i^(1<<j)^(1<<k)) << " " << dp[i^(1<<j)^(1<<k)] << "  " << j << " " << k << " : " << mat[j][k] << " " << mat[k][j] << '\n';
            }
          }
        }
      }
      //cout << i << " " << dp[i] << '\n';
    }
    cout << dp[(1<<n)-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 = 1; i <= n; ++ i){
    if (!mark[i]){
      dfs (i);
      if (sz == 2){
        sz = 0;
        continue;
      }
      ans += (sz + 1) / 2;
      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: 21 / 21
• Subtask 2: 25 / 25
• Subtask 3: 0 / 29
• Subtask 4: 0 / 25