Submission #720717

#	Time	Username	Problem	Language	Result	Execution time	Memory
720717		NeroZein	Event Hopping (BOI22_events)	C++17	0 / 100	167 ms	19004 KiB

events

#include <bits/stdc++.h>
using namespace std;

const int Log = 18; 
const int N = 100005;

int up[N][Log];

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, q;
  cin >> n >> q;
  map<int, int> mp; 
  vector<int> l(n + 1), r(n + 1); 
  vector<array<int, 3>> pts(n * 2); //L / R, idx, 0 / 1
  for (int i = 1; i <= n; ++i) {
    cin >> l[i] >> r[i];
    pts[(i - 1) * 2] = {l[i], 0, i};
    pts[(i - 1) * 2 + 1] = {r[i], 1, i};
    mp[l[i]]; mp[r[i]]; 
  }
  // int idd = 0; 
  // for (auto& it : mp) {
  //   it.second = ++idd; 
  // }
  // for (int i = 0; i < n * 2; ++i) {
  //   pts[i][0] = mp[pts[i][0]];
  // }
  sort(pts.begin(), pts.end(), [&](array<int, 3> x, array<int, 3> y) {
    return x[0] == y[0] ? x[1] < y[1] : x[0] < y[0];
  });
  // for (int i = 0; i < n * 2; ++i) {
  //   cout << pts[i][0] << ' ' << pts[i][1] << ' ' << pts[i][2] << '\n';
  // }
  int mx = 0; 
  for (int i = 0; i < n * 2; ++i) {
    if (pts[i][1] == 0) {//isL
      mx = (r[pts[i][2]] > r[mx] ? pts[i][2] : mx);
    } else {//isR
      up[pts[i][2]][0] = mx;
    }
  }
  // for (int i = 1; i <= n; ++i) {
  //   cout << up[i][0] << ' ';
  // }
  for (int i = 1; i < Log; ++i) {
    for (int j = 1; j <= n; ++j) {
      up[j][i] = up[up[j][i - 1]][i - 1];
      assert(up[j][i] != 0);
    }
  }
  auto intersect = [&]( int y, int i, int j) -> bool {
    return y >= i && y <= j;
  };
  while (q--) {
    int u, v;
    cin >> u >> v;
    if (u == v) {
      cout << 0 << '\n';
      continue;
    }
    int ans = 0; 
    for (int i = Log - 1; i >= 0; --i) {
      if (r[up[u][i]] < l[v]) {
        ans += 1 << i; 
        u = up[u][i]; 
      }
    }
    ans++;
    u = up[u][0]; 
    if (!intersect(r[u], l[v], r[v])) {
      cout << "impossible" << '\n';
    } else {
      cout << ans + 1 << '\n';
    }
  }
  return 0;
}

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