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Submission #404402

# Submission time Handle Problem Language Result Execution time Memory
404402 2021-05-14T11:18:13 Z rama_pang Alternating Current (BOI18_alternating) C++17
19 / 100
 114 ms 17180 KB 
#include <bits/stdc++.h>
using namespace std;

class Segment {
 public:
  int N;
  int index;
  int start;
  int length;
  int direction;
  int sortedIndex;
  set<Segment*> children;

  Segment(int _N, int i, int a, int b) {
    N = _N;
    index = i;
    start = a;
    length = (b + N - a) % N + 1;
    direction = 0;
    sortedIndex = -1;
    children.clear();
  }

  bool Inlude(const Segment &o) {
    int x = (o.start - start + N) % N;
    return x + o.length <= length;
  }

  void SetDirection(int dir) {
    direction = dir;
    for (auto i : children) {
      i->direction = !dir;
    }
  }
};

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);

  int N, M;
  cin >> N >> M;

  vector<Segment> segments;
  for (int i = 0; i < M; i++) {
    int a, b;
    cin >> a >> b;
    segments.emplace_back(Segment(N, i, --a, --b));
  }

  sort(begin(segments), end(segments), [&](const Segment &i, const Segment &j) {
    return i.start < j.start || (i.start == j.start && i.length > j.length);
  });

  for (int i = 0; i < M; i++) {
    segments[i].sortedIndex = i;
  }

  vector<Segment*> mainSegments;
  Segment* last = &segments[0];
  for (int i_ = 1; i_ < 2 * M; i_++) {
    int i = i_ % M;
    if (segments[i].index != last->index && last->Inlude(segments[i])) {
      last->children.emplace(&segments[i]);
    } else {
      last = &segments[i];
      if (i_ >= M) {
        mainSegments.emplace_back(&segments[i]);
      }
    }
  }

  const auto Alternating = [&](int start_) {
    for (int i_ = 0; i_ < int(mainSegments.size()); i_++) {
      int i = (i_ + start_) % mainSegments.size();
      mainSegments[i]->SetDirection(i_ % 2);
    }
  };

  if (mainSegments.size() % 2 == 0) {
    Alternating(0);
  } else {
    for (int i = 0; i < int(mainSegments.size()); i++) {
      auto S0 = mainSegments[(i + 0) % mainSegments.size()];
      auto S1 = mainSegments[(i + 1) % mainSegments.size()];
      auto S2 = mainSegments[(i + 2) % mainSegments.size()];
      auto S3 = mainSegments[(i + 3) % mainSegments.size()];

      S0->SetDirection(1);
      S1->SetDirection(0);
      S2->SetDirection(0);
      S3->SetDirection(1);

      if ([&]() -> bool {
        // Check if segment S0...S3 is good
        int cur = S0->start;
        int rep = (S3->sortedIndex - S0->sortedIndex + int(mainSegments.size()) - 1) % mainSegments.size() + 1;
        for (int i_ = 0; i_ < rep; i_++) {
          int i = (S0->sortedIndex + i_) % mainSegments.size();
          if (segments[i].direction == 0) continue;
          int st = segments[i].start;
          if (i < S0->sortedIndex) st += N;
          if (cur < st) return false;
          cur = max(cur, st + segments[i].length);
        }
        int i = S3->sortedIndex;
        int st = segments[i].start;
        if (i <= S0->sortedIndex) st += N;
        if (cur < st) return false;
        return true;
      }()) {
        Alternating((i + 2) % mainSegments.size());
        break;
      }
    }
  }

  if ([&]() -> bool {
    // Check whether solution is valid
    for (int dir = 0; dir < 2; dir++) {
      int cur = 0;
      for (int i = 0; i < 2 * M; i++) if (segments[i % M].direction == dir) {
        int st = segments[i % M].start;
        if (i < M) st -= N;
        if (cur < st) return false;
        cur = max(cur, st + segments[i % M].length);
      }
      if (cur < N) return false;
    }
    return true;
  }()) {
    vector<int> ans(M);
    for (auto seg : segments) {
      ans[seg.index] = seg.direction;
    }
    for (int i = 0; i < M; i++) {
      cout << ans[i];
    }
    cout << '\n';
  } else {
    cout << "impossible\n";
  }
  return 0;
}

Subtask #1
0 / 13.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 204 KB Output is correct
2 Correct 1 ms 204 KB Output is correct
3 Correct 1 ms 204 KB Output is correct
4 Correct 1 ms 204 KB Output is correct
5 Correct 1 ms 204 KB Output is correct
6 Correct 1 ms 204 KB Output is correct
7 Correct 1 ms 204 KB Output is correct
8 Correct 1 ms 204 KB Output is correct
9 Correct 1 ms 204 KB Output is correct
10 Correct 1 ms 204 KB Output is correct
11 Correct 1 ms 204 KB Output is correct
12 Correct 1 ms 204 KB Output is correct
13 Correct 1 ms 204 KB Output is correct
14 Correct 1 ms 204 KB Output is correct
15 Incorrect 1 ms 204 KB 'impossible' claimed, but there is a solution
16 Halted 0 ms 0 KB -

Subtask #2
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 204 KB Output is correct
2 Correct 1 ms 204 KB Output is correct
3 Correct 1 ms 204 KB Output is correct
4 Correct 1 ms 204 KB Output is correct
5 Correct 1 ms 204 KB Output is correct
6 Correct 1 ms 204 KB Output is correct
7 Correct 1 ms 204 KB Output is correct
8 Correct 1 ms 204 KB Output is correct
9 Correct 1 ms 204 KB Output is correct
10 Correct 1 ms 204 KB Output is correct
11 Correct 1 ms 204 KB Output is correct
12 Correct 1 ms 204 KB Output is correct
13 Correct 1 ms 204 KB Output is correct
14 Correct 1 ms 204 KB Output is correct
15 Incorrect 1 ms 204 KB 'impossible' claimed, but there is a solution
16 Halted 0 ms 0 KB -

Subtask #3
0 / 22.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 204 KB Output is correct
2 Correct 1 ms 204 KB Output is correct
3 Correct 1 ms 204 KB Output is correct
4 Correct 1 ms 204 KB Output is correct
5 Correct 1 ms 204 KB Output is correct
6 Correct 1 ms 204 KB Output is correct
7 Correct 1 ms 204 KB Output is correct
8 Correct 1 ms 204 KB Output is correct
9 Correct 1 ms 204 KB Output is correct
10 Correct 1 ms 204 KB Output is correct
11 Correct 1 ms 204 KB Output is correct
12 Correct 1 ms 204 KB Output is correct
13 Correct 1 ms 204 KB Output is correct
14 Correct 1 ms 204 KB Output is correct
15 Incorrect 1 ms 204 KB 'impossible' claimed, but there is a solution
16 Halted 0 ms 0 KB -

Subtask #4
19.0 / 19.0

# Verdict Execution time Memory Grader output
1 Correct 114 ms 17180 KB Output is correct
2 Correct 1 ms 204 KB Output is correct
3 Correct 39 ms 6168 KB Output is correct
4 Correct 46 ms 8688 KB Output is correct
5 Correct 68 ms 10488 KB Output is correct
6 Correct 60 ms 11160 KB Output is correct
7 Correct 70 ms 10872 KB Output is correct
8 Correct 2 ms 700 KB Output is correct
9 Correct 1 ms 332 KB Output is correct
10 Correct 67 ms 10920 KB Output is correct
11 Correct 54 ms 9712 KB Output is correct
12 Correct 97 ms 15524 KB Output is correct
13 Correct 1 ms 204 KB Output is correct
14 Correct 1 ms 204 KB Output is correct
15 Correct 102 ms 17164 KB Output is correct
16 Correct 21 ms 5056 KB Output is correct
17 Correct 99 ms 15444 KB Output is correct
18 Correct 104 ms 16672 KB Output is correct
19 Correct 4 ms 936 KB Output is correct
20 Correct 78 ms 10696 KB Output is correct

Subtask #5
0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 204 KB Output is correct
2 Correct 1 ms 204 KB Output is correct
3 Correct 1 ms 204 KB Output is correct
4 Correct 1 ms 204 KB Output is correct
5 Correct 1 ms 204 KB Output is correct
6 Correct 1 ms 204 KB Output is correct
7 Correct 1 ms 204 KB Output is correct
8 Correct 1 ms 204 KB Output is correct
9 Correct 1 ms 204 KB Output is correct
10 Correct 1 ms 204 KB Output is correct
11 Correct 1 ms 204 KB Output is correct
12 Correct 1 ms 204 KB Output is correct
13 Correct 1 ms 204 KB Output is correct
14 Correct 1 ms 204 KB Output is correct
15 Incorrect 1 ms 204 KB 'impossible' claimed, but there is a solution
16 Halted 0 ms 0 KB -