Submission #1166921

#	Time	Username	Problem	Language	Result	Execution time	Memory
1166921		fryingduc	Event Hopping (BOI22_events)	C++20	30 / 100	71 ms	15288 KiB

events

#include "bits/stdc++.h"

using namespace std;

#ifdef duc_debug
#include "bits/debug.h"
#else
#define debug(...)
#endif

const int maxn = 3e5 + 5;
const int LG = 19;
int n, q;
int sl[maxn], sr[maxn];
int ord[maxn];
int up[maxn][LG + 1];

void solve() {
  cin >> n >> q;
  vector<pair<int, int>> ev;
  for (int i = 1; i <= n; ++i) {
    cin >> sl[i] >> sr[i];
    ev.emplace_back(sr[i], i);
    ev.emplace_back(sl[i] - 1, -i);
  }
  sort(ev.begin(), ev.end(), [](const pair<int, int> &x, const pair<int, int> &y) -> bool {
    if (x.first != y.first) return x.first > y.first;
    return (x.second < y.second);
  });
  set<pair<int, int>> s;
  for (int i = 0; i < (int)ev.size(); ++i) {
    int cur = 0;
    while (i + cur < (int)ev.size() and ev[i].first == ev[i + cur].first) ++cur;
    for (int j = i; j < i + cur; ++j) {
      if (ev[j].second < 0) {
        int t = -ev[j].second;
        s.erase(s.find(make_pair(sr[t], t)));
      } else {
        s.insert(make_pair(sr[ev[j].second], ev[j].second));
        auto it = s.rbegin();
        if (ev[j].second != it->second) {
          up[ev[j].second][0] = it->second;
        }
      }
    }
    i = i + cur - 1;
  }
  for (int j = 1; j <= LG; ++j) {
    for (int i = 1; i <= n; ++i) {
      up[i][j] = up[up[i][j - 1]][j - 1];
    }
  }
  while (q--) {
    int s, e; cin >> s >> e;
    if (s == e) {
      cout << 0 << '\n';
      continue;
    }
    if (sr[e] < sr[s]) {
      cout << "impossible\n";
      continue;
    }
    int ans = 0;
    int cur = s;
    for (int i = LG; i >= 0; --i) {
      if (up[cur][i] and sr[up[cur][i]] < sr[e]) {
        ans ^= (1 << i);
        cur = up[cur][i];
      }
    }
    if (sl[e] <= sr[cur]) cout << ans + 1 << '\n';
    else {
//      debug(cur, up[cur][0]);
      cur = up[cur][0];
      if (!cur || sr[cur] > sr[e]) cout << "impossible\n";
      else cout << ans + 2 << '\n';
    }
  }
}

signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  solve();

  return 0;
}

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