Submission #1001331

#	Time	Username	Problem	Language	Result	Execution time	Memory
1001331		spacewalker	Longest Trip (IOI23_longesttrip)	C++17	5 / 100	7 ms	424 KiB

longesttrip

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

using namespace std;

optional<int> find_edge_between(vector<int> s, int v) {
  if (!are_connected(s, {v})) return nullopt;
  vector<int> current = s;
  while (current.size() > 1) {
    int hs = current.size() / 2;
    vector<int> h1(begin(current), begin(current) + hs), h2(begin(current) + hs, end(current));
    if (are_connected(h1, {v})) current = h1;
    else current = h2;
  }
  return current[0];
}

optional<pair<int, int>> find_edge_between(vector<int> s1, vector<int> s2) {
  if (!are_connected(s1, s2)) return nullopt;
  vector<int> current = s1;
  while (current.size() > 1) {
    int hs = current.size() / 2;
    vector<int> h1(begin(current), begin(current) + hs), h2(begin(current) + hs, end(current));
    if (are_connected(h1, s2)) current = h1;
    else current = h2;
  }
  return make_pair(current[0], find_edge_between(s2, current[0]).value());
}

std::vector<int> longest_trip(int N, int D) {
  deque<int> p1{0}, p2;
  for (int i = 1; i < N; ++i) {
    if (are_connected({p1.back()}, {i})) {
      p1.push_back(i);
    } else if (!p2.empty()) {
      p2.push_front(i);
    } else {
      p2.push_back(i);
    }
  }
  vector<int> fp1(p1.begin(), p1.end()), fp2(p2.begin(), p2.end());
  if (fp1.size() == N) return fp1;
  if (!are_connected({fp2.front()}, {fp2.back()})) {
    vector<int> ans = fp1;
    reverse(begin(fp2), end(fp2));
    ans.insert(end(ans), begin(fp2), end(fp2));
    return ans;
  }
  if (!are_connected({fp1.front()}, {fp1.back()})) {
    vector<int> ans = fp2;
    reverse(begin(fp2), end(fp2));
    ans.insert(end(ans), begin(fp1), end(fp1));
    return ans;
  }

  auto bridge = find_edge_between(fp1, fp2);
  if (!bridge) {
    return fp1.size() > fp2.size() ? fp1 : fp2;
  }

  auto left_end_iter = find(begin(fp2), end(fp2), bridge->second);
  rotate(begin(fp2), left_end_iter, end(fp2));

  auto right_end_iter = find(begin(fp1), end(fp1), bridge->first);
  rotate(begin(fp1), right_end_iter, end(fp1));

  vector<int> ans = fp2;
  reverse(begin(ans), end(ans));
  ans.insert(end(ans), begin(fp1), end(fp1));
  return ans;

  
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:42:18: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   42 |   if (fp1.size() == N) return fp1;
      |       ~~~~~~~~~~~^~~~

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