Submission #1037898

#	Time	Username	Problem	Language	Result	Execution time	Memory
1037898		erray	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	18 ms	760 KiB

longesttrip

#include "longesttrip.h"
#include <bits/stdc++.h>

using namespace std;

#ifdef DEBUG 
  #include "/home/ioi/egoi2024/d2/debug.h"
#else 
  #define debug(...) void(37)
#endif

vector<int> m(vector<int> x, vector<int> y) {
  vector<int> res;
  res = x;
  res.insert(res.end(), y.begin(), y.end());
  return res;
}


mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

std::vector<int> longest_trip(int N, int D) {
  array<vector<int>, 2> l{};
  vector<int> ord(N);
  iota(ord.begin(), ord.end(), 0);
  shuffle(ord.begin(), ord.end(), rng);
  l[0] = {ord.back()};
  ord.pop_back();
  for (auto i : ord) {
    if (l[1].empty()) {
      l[1].push_back(i);
    } else if (are_connected({i}, {l[0].back()})) {
      l[0].push_back(i);
    } else if (are_connected({i}, {l[1].back()})) {
      l[1].push_back(i);
    } else {
      l[0] = m(l[0], l[1]);
      l[1] = {i};
    }
  }
  if (l[1].empty()) return l[0];
  vector<int> ans;
  for (int it = 0; it < 2; ++it) {
    for (int it1 = 0; it1 < 2; it1++) {
      if (are_connected({l[0].back()}, {l[1][0]})) {
        ans = m(l[0], l[1]);
      }
      reverse(l[1].begin(), l[1].end());
    }
    swap(l[0], l[1]);
  }
  if (ans.empty()) {
    if (!are_connected(l[0], l[1])) {
      ans = int(l[0].size()) > int(l[1].size()) ? l[0] : l[1];
    } else {
      int s = -1;
      {
        int low = 0, high = int(l[1].size()) - 1;
        while (low < high) {
          int mid = (low + high) >> 1;
          if (are_connected(l[0], vector<int>(l[1].begin(), l[1].begin() + mid + 1))) {
            high = mid;
          } else {
            low = mid + 1;
          }
        }
        s = low;
      }
      int f = -1;
      {
        int low = 0, high = int(l[0].size()) - 1;
        while (low < high) {
          int mid = (low + high) >> 1;
          if (are_connected({l[1][s]}, vector<int>(l[0].begin(), l[0].begin() + mid + 1))) {
            high = mid;
          } else {
            low = mid + 1;
          }
        }
        f = low;
      }
      rotate(l[1].begin(), l[1].begin() + s, l[1].end());
      if (f != int(l[0].size()) - 1) rotate(l[0].begin(), l[0].begin() + f + 1, l[0].end());
      ans = m(l[0], l[1]);
    }
  } 
  return ans;
}

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 60