Submission #1229332

#	Time	Username	Problem	Language	Result	Execution time	Memory
1229332		avighna	Event Hopping (BOI22_events)	C++20	0 / 100	157 ms	6784 KiB

events

#include <bits/stdc++.h>

int main() {
  int n, q;
  std::cin >> n >> q;
  struct time {
    int s, e;
  };
  std::vector<time> a(n);
  for (auto &[s, e] : a) {
    std::cin >> s >> e;
  }

  auto comp = [](time a, time b) {
    return a.s < b.s;
  };
  std::sort(a.begin(), a.end(), comp);
  std::vector<std::pair<time, int>> suff(n);
  suff[n - 1] = {a[n - 1], n - 1};
  for (int i = n - 2; i >= 0; --i) {
    suff[i] = suff[i + 1];
    if (a[i].e < suff[i].first.e) { 
      suff[i] = {a[i], i};
    }
  }

  int tot_comps = 0, timer = 0;
  std::vector<int> comp_num(n), start(n);
  auto dfs = [&](auto &&self, int u) {
    start[u] = timer++;
    time t = {a[u].e, 0};
    auto it = std::lower_bound(a.begin(), a.end(), t, comp);
    int idx = suff[it - a.begin()].second;
    if (it == a.end() or a[u].e > a[idx].e) {
      comp_num[u] = tot_comps++;
      return;
    }
    self(self, idx);
    comp_num[u] = comp_num[idx];
  };
  dfs(dfs, 0);

  while (q--) {
    int beg, end;
    std::cin >> beg >> end;
    if (comp_num[beg] != comp_num[end] or start[beg] > start[end]) {
      std::cout << "impossible\n";
    } else {
      std::cout << start[end] - start[beg] << '\n';
    }
  }
}

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30