Submission #1001346

#	Time	Username	Problem	Language	Result	Execution time	Memory
1001346		spacewalker	Longest Trip (IOI23_longesttrip)	C++17	100 / 100	12 ms	612 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;
  bool sure_ps_are_dced = true;
  for (int i = 1; i < N; ++i) {
    if (are_connected({p1.back()}, {i})) {
      p1.push_back(i);
      if (!p2.empty()) sure_ps_are_dced = false;
    } else if (p2.empty()) {
      p2.push_front(i);
      sure_ps_are_dced = true;
    } else {
      bool ps_are_dced = sure_ps_are_dced || !are_connected({p1.back()}, {p2.front()});
      if (ps_are_dced) {
        p2.push_front(i);
        sure_ps_are_dced = true;
      } else {
        p1.insert(end(p1), begin(p2), end(p2));
        p2.clear();
        --i; // we will have to process this again
      }
    }
    /*
    cerr << "adding " << i << endl;
    for (int v : p1) cerr << v << " ";
    cerr << (sure_ps_are_dced ? " X " : " ? ");
    for (int v : p2) cerr << v << " ";
    cerr << endl;
    */
  }
  if (!sure_ps_are_dced && !p2.empty() && are_connected({p1.back()}, {p2.front()})) {
      p1.insert(end(p1), begin(p2), end(p2));
      return vector(begin(p1), end(p1)); 
  }
  vector<int> fp1(p1.begin(), p1.end()), fp2(p2.begin(), p2.end());
  if (fp1.size() == N) return fp1;
  if (fp2.size() > 1 && !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 (fp1.size() > 1 && !are_connected({fp1.front()}, {fp1.back()})) {
    reverse(begin(fp2), end(fp2));
    vector<int> ans = 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:64:18: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   64 |   if (fp1.size() == N) return fp1;
      |       ~~~~~~~~~~~^~~~

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