Submission #887094

#	Time	Username	Problem	Language	Result	Execution time	Memory
887094		peterandvoi	Event Hopping (BOI22_events)	C++17	10 / 100	1522 ms	99532 KiB

events

#include <bits/stdc++.h>

using namespace std;

#define db(...) " [" << #__VA_ARGS__ << " : " << (__VA_ARGS__) << "] "

const int N = 100005;

int n, q;
int s[N], e[N], p[N];

namespace sub3 {
  bool valid_input() {
    return n <= 5000;
  }
  
  int dp[5005][5005];
  
  void solve() {
    multiset<int> cur;
    priority_queue<pair<int, int>> pq;
    for (int i = 1; i <= n; ++i) {
      for (int j = 1; j <= n; ++j) {
        dp[i][j] = 1e9;
      }
    }
    for (int i = 1; i <= n; ++i) {
      while (pq.size()) {
        pq.pop();
      }
      cur.clear();
      dp[p[i]][p[i]] = 0; // just to remember
      cur.insert(0);
      pq.emplace(s[p[i]], p[i]);
      for (int j = i - 1; j >= 1; --j) {
        int &res = dp[p[j]][p[i]];
        while (pq.size() && pq.top().first > e[p[j]]) {
          cur.erase(cur.find(dp[pq.top().second][p[i]]));
          pq.pop();
        }
        if (cur.size()) {
          res = min(res, *cur.begin() + 1);
        }
        cur.insert(res);
        pq.emplace(s[p[j]], p[j]);
      }
    }
    while (q--) {
      int s, t;
      cin >> s >> t;
      if (dp[s][t] == 1e9) {
        cout << "impossible\n";
      } else {
        cout << dp[s][t] << '\n';
      }
    }
  }
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> q;
  for (int i = 1; i <= n; ++i) {
    cin >> s[i] >> e[i];
  }
  vector<int> ord(n);
  iota(ord.begin(), ord.end(), 1);
  sort(ord.begin(), ord.end(), [&](int x, int y) {
    return e[x] == e[y] ? s[x] < s[y] : e[x] < e[y];
  });
  for (int i = 0; i < n; ++i) {
    p[i + 1] = ord[i];
  }
  if (sub3::valid_input()) {
    sub3::solve();
  }
}

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