Submission #987777

#	Time	Username	Problem	Language	Result	Execution time	Memory
987777		MilosMilutinovic	Love Polygon (BOI18_polygon)	C++14	0 / 100	350 ms	21072 KiB

polygon

#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> to(n);
  map<string, int> mp;
  for (int i = 0; i < n; i++) {
    string s;
    cin >> s;
    string t;
    cin >> t;
    if (!mp.count(s)) {
      mp[s] = (int) mp.size();
    }
    if (!mp.count(t)) {
      mp[t] = (int) mp.size();
    }
    to[mp[s]] = mp[t];
  }
  if (n % 2 == 1) {
    cout << -1 << '\n';
    return 0;
  }
  vector<vector<int>> ch(n);
  for (int i = 0; i < n; i++) {
    if (to[i] == i) {
      continue;
    }
    ch[to[i]].push_back(i);
  }
  vector<int> deg(n);
  for (int i = 0; i < n; i++) {
    deg[to[i]] += 1;
  }
  vector<int> que;
  for (int i = 0; i < n; i++) {
    if (deg[i] == 0) {
      que.push_back(i);
    }
  }
  for (int b = 0; b < (int) que.size(); b++) {
    int i = que[b];
    deg[to[i]] -= 1;
    if (deg[to[i]] == 0) {
      que.push_back(to[i]);
    }
  }
  vector<vector<int>> dp(n, vector<int>(2));
  function<void(int)> Solve = [&](int v) {
    int mx = 0;
    for (int u : ch[v]) {
      Solve(u);
      dp[v][0] += max(dp[u][0], dp[u][1]);
      dp[v][1] += dp[u][0];
      mx = max(mx, -dp[u][0] + dp[u][1] + 1);
    }
    dp[v][1] += mx;
  };
  int res = 0;
  for (int b = 0; b < (int) que.size(); b++) {
    int i = que[b];
    Solve(i);
    res += dp[i][1]; 
  }
  cout << (n - 2 * res) + res << '\n';
  return 0;
}

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