Submission #635928

#	Time	Username	Problem	Language	Result	Execution time	Memory
635928		Kanon	Thousands Islands (IOI22_islands)	C++17	100 / 100	439 ms	45116 KiB

islands

#include <bits/stdc++.h>

using namespace std;

template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__);

struct edge {
  int from;
  int to;
  edge(){};
  edge(int _from, int _to) : from(_from), to(_to){};
};

variant<bool, vector<int>> find_journey(int n, int m, vector<int> A, vector<int> B) {
  vector<edge> edges;
  vector<set<int>> g(n);
  vector<set<int>> rev_g(n);

  auto rev = [&](int e) {
    int u = edges[e].from, v = edges[e].to;
    g[u].erase(e);
    rev_g[v].erase(e);
  };
  auto add = [&](int e) {
    int u = edges[e].from, v = edges[e].to;
    g[u].insert(e);
    rev_g[v].insert(e);
  };

  for (int i = 0; i < m; i++) {
    edges.emplace_back(A[i], B[i]);
    add(i);
  }

  int st = 0;
  vector<int> trail;
  set<pair<int, int>> pos;
  for (int i = 0; i < n; i++) {
    pos.insert(make_pair(g[i].size(), i));
  }

  while (true) {
    bool change = false;
    while (pos.size() && pos.begin()->first == 0) {
      int v = pos.begin()->second;

      pos.erase(pos.begin());
      change = true;
      vector<int> make;
      for (int e : rev_g[v]) {
        make.push_back(e);
      }
      for (int e : make) {
        int u = edges[e].from;
        pos.erase(make_pair(g[u].size(), u));
        rev(e);
        pos.insert(make_pair(g[u].size(), u));
      }
    }
    while (g[st].size() < 2) {
      if (g[st].empty()) {
        return false;
      }
      vector<int> make;
      for (int e : rev_g[st]) {
        make.push_back(e);
      }
      for (int e : make) {
        if (trail.size() && e == trail.back()) {
          continue;
        }
        change = true;
        int u = edges[e].from;
        pos.erase(make_pair(g[u].size(), u));
        rev(e);
        pos.insert(make_pair(g[u].size(), u));
      }
      int e = *g[st].begin();
      st = edges[e].to;
      trail.push_back(e);
    }
    if (!change) {
      break;
    }
  }

  vector<int> path;
  vector<int> cyc;
  vector<bool> was(n);
  vector<bool> in_queque(n);
  vector<int> que;
  vector<int> ed;
  function<bool(int)> dfs = [&](int v) {
    was[v] = true;
    in_queque[v] = true;
    que.push_back(v);
    for (int e : g[v]) {
      int u = edges[e].to;
      if (in_queque[u]) {
        bool done = false;
        for (int es : ed) {
          if (edges[es].from != u && !done) {
            path.push_back(es);
          } else {
            cyc.push_back(es);
            done = true;
          }
        }
        cyc.push_back(e);
        return true;
      }
      if (was[u]) {
        continue;
      }
      ed.push_back(e);
      if (dfs(u)) {
        return true;
      }
      ed.pop_back();
    }
    in_queque[v] = false;
    que.pop_back();
    return false;
  };

  vector<int> path1, path2, cyc1, cyc2;
  if (!dfs(st)) {
    return false;
  }
  path1 = path;
  cyc1 = cyc;
  fill(in_queque.begin(), in_queque.end(), false);
  fill(was.begin(), was.end(), false);
  path.clear();
  cyc.clear();
  que.clear();
  ed.clear();
  for (int e : cyc1) {
    rev(e);
    swap(edges[e].from, edges[e].to);
    add(e);
  }
  for (int e : cyc1) {
    int v = edges[e].from;
    vector<int> r;
    if (v != st) {
      for (int es : g[v]) {
        if (es != e) {
          r.push_back(es);
        }
      }
    } else {
      assert(path1.empty());
    }
    for (int es : r) {
      rev(es);
    }
  }
  if (path1.empty()) {
    for (int e : cyc1) {
      int v = edges[e].from;
      if (v == st) {
        for (int es : g[v]) {
          if (es == e) {
            continue;
          }
          int u = edges[es].to;
          vector<int> make;
          for (int E : g[v]) {
            if (E != e) {
              make.push_back(E);
            }
          }
          for (int E : make) {
            rev(E);
          }
          assert(dfs(u));
          path2 = path;
          cyc2 = cyc;
          path2.insert(path2.begin(), es);
          break;
        }
        assert(cyc2.size() && path2.size());
        break;
      }
    }
  } else {
    int e = path1[0];
    assert(edges[e].from == st);
    rev(e);
    assert(dfs(st));
    path2 = path;
    cyc2 = cyc;
  }
  vector<int> ret;
  auto add_way = [&](vector<int> &a) {
    for (int e : a) {
      ret.push_back(e);
    }
    reverse(a.begin(), a.end());
  };
  bool same = false;
  {
    int sam = edges[cyc1[0]].from;
    for (int e : cyc2) {
      int v = edges[e].from;
      if (v == sam) {
        same = true;
      }
    }
  }
  add_way(trail);
  for (int rot = 0; rot < (same ? 1 : 2); rot++) {
    add_way(path1);
    add_way(cyc1);
    add_way(path1);
    add_way(path2);
    add_way(cyc2);
    add_way(path2);
  }
  add_way(trail);
  return ret;
}

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 21 / 21
• Subtask 4: 24 / 24
• Subtask 5: 45 / 45