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Submission #844813

# Submission time Handle Problem Language Result Execution time Memory
844813 2023-09-06T01:38:28 Z obokaman Event Hopping (BOI22_events) C++17
100 / 100
 269 ms 14256 KB 
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

typedef pair<int, int> PII;

int main() {
  int N, Q;
  cin >> N >> Q;
  vector<PII> ints(N);
  for (int i = 0; i < N; ++i) {
    cin >> ints[i].first >> ints[i].second;
  }
  vector<PII> sweep(2 * N);
  for (int i = 0; i < N; ++i) {
    sweep[2 * i] = {ints[i].first, i};
    // We need all closing to appear after all opening.
    sweep[2 * i + 1] = {ints[i].second, N + i};
  }
  sort(sweep.begin(), sweep.end());

  vector<int> parent(N);
  vector<int> anc(17 * N);
  // {closing pos, index}, sorted decreasing closing pos. In addition, we
  // only keep those candidates that are useful: the ones that have smallest
  // open positions are allowed to have largest closing pos.
  vector<PII> candidates;
  for (int i = 2 * N - 1; i >= 0; --i) {
    auto& p = sweep[i];
    bool close = p.second >= N;
    int x = p.second % N;  // index

    if (close) {  // [?, ints[x].second]
      //      cout << "[?, " << ints[x].second << "]" << endl;
      // remove useless candidate, add new candidate
      while (!candidates.empty()) {
        auto& c = candidates.back();
        if (ints[x].first <= ints[c.second].first) {
          candidates.pop_back();
        } else {
          break;
        }
      }
      if (candidates.empty() ||
          ints[x].second < ints[candidates.back().second].second) {
        candidates.emplace_back(ints[x].second, x);
      }
      // //      cout << "candidates: ";
      // for (auto& c : candidates) {
      //   cout << c.first << "," << c.second << " ";
      // }
      // cout << endl;
    } else {  // [ints[x].first, ?]
      //      cout << "[" << ints[x].first << ",?]" << endl;
      // We compute x's parent: the candidate with largest second, but
      // smaller or equal than x's second.

      // (careful: we are using greater; also, since we will never match,
      // we don't care whether to use upper_bound or lower_bound). This
      // returns the left-most valid candidate, or .end() if it does not exist.
      auto it = upper_bound(candidates.begin(), candidates.end(),
                            PII{ints[x].second + 1, -1}, greater<PII>());
      if (it == candidates.end()) {
        parent[x] = x;  // all are invalid
      } else {
        //        cout << "Trobat it: " << it->first << "," << it->second <<
        //        endl;
        parent[x] = it->second;
      }
    }
  }
  // for (int i = 0; i < N; ++i) {
  //   cout << "parent " << i << ": " << parent[i] << endl;
  // }
  for (int i = 0; i < N; ++i) {
    anc[i] = parent[i];
  }
  for (int lev = 1; lev < 17; ++lev) {
    for (int i = 0; i < N; ++i) {
      anc[lev * N + i] = anc[(lev - 1) * N + anc[(lev - 1) * N + i]];
    }
  }

  //  for (int lev = 0; lev < 17; ++lev) {
  //   for (int i = 0; i < N; ++i) {
  //     cout << " " << anc[lev * N + i];
  //   }
  //   cout << endl;
  // }
  // cout << endl;
  for (int i = 0; i < Q; ++i) {
    int s, e;
    cin >> s >> e;
    --s;
    --e;
    if (s == e) {
      cout << 0 << endl;
    } else if (ints[e].first <= ints[s].second &&
               ints[s].second <= ints[e].second) {
      cout << 1 << endl;
    } else if (ints[s].second > ints[e].second) {
      cout << "impossible" << endl;
    } else {
      int x = e;
      int steps = 0;
      for (int l = 16; l >= 0; --l) {
        //        cout << x << ": ";
        int x2 = anc[l * N + x];
        if (ints[s].second < ints[x2].first) {
          // x guaranteed to never contain s.
          x = x2;
          steps += (1 << l);
        }
        // cout << x << "... ";
      }
      //      cout << endl;
      if (parent[x] != x) {
        // 1 extra step possible
        cout << (steps + 2) << endl;
      } else {
        cout << "impossible" << endl;
      }
    }
  }
}

Subtask #1
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 234 ms 11204 KB Output is correct
3 Correct 261 ms 13488 KB Output is correct
4 Correct 262 ms 13728 KB Output is correct
5 Correct 253 ms 13612 KB Output is correct
6 Correct 246 ms 13584 KB Output is correct
7 Correct 247 ms 13604 KB Output is correct
8 Correct 255 ms 14036 KB Output is correct
9 Correct 251 ms 13904 KB Output is correct
10 Correct 255 ms 14120 KB Output is correct
11 Correct 249 ms 13800 KB Output is correct
12 Correct 211 ms 13136 KB Output is correct

Subtask #2
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 344 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 344 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 1 ms 460 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 344 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 344 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 1 ms 460 KB Output is correct
10 Correct 0 ms 344 KB Output is correct
11 Correct 0 ms 348 KB Output is correct
12 Correct 2 ms 348 KB Output is correct
13 Correct 1 ms 344 KB Output is correct
14 Correct 1 ms 348 KB Output is correct
15 Correct 1 ms 460 KB Output is correct
16 Correct 1 ms 460 KB Output is correct
17 Correct 1 ms 348 KB Output is correct
18 Correct 1 ms 348 KB Output is correct
19 Correct 161 ms 2032 KB Output is correct
20 Correct 158 ms 2028 KB Output is correct
21 Correct 171 ms 2596 KB Output is correct
22 Correct 156 ms 2640 KB Output is correct
23 Correct 154 ms 2492 KB Output is correct
24 Correct 157 ms 2384 KB Output is correct
25 Correct 154 ms 2132 KB Output is correct

Subtask #4
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 344 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 344 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 1 ms 460 KB Output is correct
10 Correct 0 ms 348 KB Output is correct
11 Correct 0 ms 348 KB Output is correct
12 Correct 1 ms 348 KB Output is correct
13 Correct 1 ms 348 KB Output is correct
14 Correct 1 ms 348 KB Output is correct
15 Correct 1 ms 348 KB Output is correct
16 Correct 1 ms 348 KB Output is correct
17 Correct 1 ms 348 KB Output is correct
18 Correct 1 ms 348 KB Output is correct
19 Correct 74 ms 11060 KB Output is correct
20 Correct 63 ms 10428 KB Output is correct
21 Correct 75 ms 10940 KB Output is correct
22 Correct 74 ms 11088 KB Output is correct
23 Correct 73 ms 10968 KB Output is correct
24 Correct 75 ms 11092 KB Output is correct
25 Correct 52 ms 10436 KB Output is correct

Subtask #5
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 236 ms 11208 KB Output is correct
2 Correct 253 ms 13472 KB Output is correct
3 Correct 263 ms 13404 KB Output is correct
4 Correct 253 ms 13908 KB Output is correct
5 Correct 250 ms 13856 KB Output is correct
6 Correct 251 ms 13588 KB Output is correct
7 Correct 255 ms 13776 KB Output is correct
8 Correct 240 ms 13636 KB Output is correct
9 Correct 73 ms 11696 KB Output is correct
10 Correct 240 ms 13116 KB Output is correct
11 Correct 231 ms 13104 KB Output is correct
12 Correct 243 ms 13100 KB Output is correct

Subtask #6
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 234 ms 11204 KB Output is correct
3 Correct 261 ms 13488 KB Output is correct
4 Correct 262 ms 13728 KB Output is correct
5 Correct 253 ms 13612 KB Output is correct
6 Correct 246 ms 13584 KB Output is correct
7 Correct 247 ms 13604 KB Output is correct
8 Correct 255 ms 14036 KB Output is correct
9 Correct 251 ms 13904 KB Output is correct
10 Correct 255 ms 14120 KB Output is correct
11 Correct 249 ms 13800 KB Output is correct
12 Correct 211 ms 13136 KB Output is correct
13 Correct 0 ms 348 KB Output is correct
14 Correct 0 ms 348 KB Output is correct
15 Correct 1 ms 348 KB Output is correct
16 Correct 1 ms 344 KB Output is correct
17 Correct 1 ms 348 KB Output is correct
18 Correct 1 ms 348 KB Output is correct
19 Correct 1 ms 344 KB Output is correct
20 Correct 1 ms 348 KB Output is correct
21 Correct 1 ms 460 KB Output is correct
22 Correct 0 ms 344 KB Output is correct
23 Correct 0 ms 348 KB Output is correct
24 Correct 2 ms 348 KB Output is correct
25 Correct 1 ms 344 KB Output is correct
26 Correct 1 ms 348 KB Output is correct
27 Correct 1 ms 460 KB Output is correct
28 Correct 1 ms 460 KB Output is correct
29 Correct 1 ms 348 KB Output is correct
30 Correct 1 ms 348 KB Output is correct
31 Correct 161 ms 2032 KB Output is correct
32 Correct 158 ms 2028 KB Output is correct
33 Correct 171 ms 2596 KB Output is correct
34 Correct 156 ms 2640 KB Output is correct
35 Correct 154 ms 2492 KB Output is correct
36 Correct 157 ms 2384 KB Output is correct
37 Correct 154 ms 2132 KB Output is correct
38 Correct 0 ms 348 KB Output is correct
39 Correct 0 ms 348 KB Output is correct
40 Correct 1 ms 348 KB Output is correct
41 Correct 1 ms 348 KB Output is correct
42 Correct 1 ms 348 KB Output is correct
43 Correct 1 ms 348 KB Output is correct
44 Correct 1 ms 348 KB Output is correct
45 Correct 1 ms 348 KB Output is correct
46 Correct 1 ms 348 KB Output is correct
47 Correct 74 ms 11060 KB Output is correct
48 Correct 63 ms 10428 KB Output is correct
49 Correct 75 ms 10940 KB Output is correct
50 Correct 74 ms 11088 KB Output is correct
51 Correct 73 ms 10968 KB Output is correct
52 Correct 75 ms 11092 KB Output is correct
53 Correct 52 ms 10436 KB Output is correct
54 Correct 236 ms 11208 KB Output is correct
55 Correct 253 ms 13472 KB Output is correct
56 Correct 263 ms 13404 KB Output is correct
57 Correct 253 ms 13908 KB Output is correct
58 Correct 250 ms 13856 KB Output is correct
59 Correct 251 ms 13588 KB Output is correct
60 Correct 255 ms 13776 KB Output is correct
61 Correct 240 ms 13636 KB Output is correct
62 Correct 73 ms 11696 KB Output is correct
63 Correct 240 ms 13116 KB Output is correct
64 Correct 231 ms 13104 KB Output is correct
65 Correct 243 ms 13100 KB Output is correct
66 Correct 0 ms 348 KB Output is correct
67 Correct 247 ms 13396 KB Output is correct
68 Correct 245 ms 13340 KB Output is correct
69 Correct 269 ms 13512 KB Output is correct
70 Correct 244 ms 13392 KB Output is correct
71 Correct 253 ms 13908 KB Output is correct
72 Correct 244 ms 13800 KB Output is correct
73 Correct 247 ms 13864 KB Output is correct
74 Correct 250 ms 14256 KB Output is correct
75 Correct 249 ms 13908 KB Output is correct
76 Correct 258 ms 13904 KB Output is correct
77 Correct 207 ms 13216 KB Output is correct
78 Correct 1 ms 348 KB Output is correct
79 Correct 1 ms 348 KB Output is correct
80 Correct 1 ms 348 KB Output is correct
81 Correct 1 ms 348 KB Output is correct
82 Correct 1 ms 448 KB Output is correct
83 Correct 1 ms 464 KB Output is correct
84 Correct 1 ms 460 KB Output is correct
85 Correct 1 ms 348 KB Output is correct
86 Correct 159 ms 2360 KB Output is correct
87 Correct 169 ms 2400 KB Output is correct
88 Correct 169 ms 2644 KB Output is correct
89 Correct 163 ms 2696 KB Output is correct
90 Correct 156 ms 2492 KB Output is correct
91 Correct 161 ms 2452 KB Output is correct
92 Correct 155 ms 2144 KB Output is correct
93 Correct 75 ms 11604 KB Output is correct
94 Correct 59 ms 10840 KB Output is correct
95 Correct 75 ms 11600 KB Output is correct
96 Correct 74 ms 11608 KB Output is correct
97 Correct 72 ms 11620 KB Output is correct
98 Correct 72 ms 11600 KB Output is correct
99 Correct 53 ms 10932 KB Output is correct
100 Correct 249 ms 13848 KB Output is correct
101 Correct 240 ms 13488 KB Output is correct
102 Correct 237 ms 13724 KB Output is correct
103 Correct 243 ms 13140 KB Output is correct
104 Correct 236 ms 13120 KB Output is correct
105 Correct 241 ms 13304 KB Output is correct
106 Correct 230 ms 12884 KB Output is correct
107 Correct 261 ms 12928 KB Output is correct
108 Correct 238 ms 13548 KB Output is correct
109 Correct 240 ms 13608 KB Output is correct
110 Correct 245 ms 13560 KB Output is correct
111 Correct 234 ms 13396 KB Output is correct