Submission #958913

#	Time	Username	Problem	Language	Result	Execution time	Memory
958913		nguyentunglam	Longest Trip (IOI23_longesttrip)	C++17	100 / 100	14 ms	1116 KiB

longesttrip

#include "longesttrip.h"
#ifdef ngu
#include "grader.cpp"
#endif // ngu
#include<bits/stdc++.h>
using namespace std;

pair<int, int> Find (vector<int> a, vector<int> b) {
  if (!are_connected(a, b)) return make_pair(-1, -1);
  int l = 0, r = a.size() - 1, lastx = -1, lasty = -1;
  while (l <= r) {
    int mid = l + r >> 1;
    vector<int> ask;
    for(int i = 0; i <= mid; i++) ask.push_back(a[i]);
    if (are_connected(ask, b)) {
      lastx = mid;
      r = mid - 1;
    } else l = mid + 1;
  }
  l = 0, r = b.size() - 1;
  while (l <= r) {
    int mid = l + r >> 1;
    vector<int> ask;
    for(int i = 0; i <= mid; i++) ask.push_back(b[i]);
    if (are_connected(ask, {a[lastx]})) {
      lasty = mid;
      r = mid - 1;
    } else l = mid + 1;
  }
  assert(are_connected({a[lastx]}, {b[lasty]}));
  return make_pair(lastx, lasty);
}

vector<int> rev (vector<int> a) {
  reverse(a.begin(), a.end());
  return a;
}

vector<int> sum (vector<int> a, vector<int> b) {
  for(int &j : b) a.push_back(j);
  return a;
}

std::vector<int> longest_trip(int n, int d)
{
    vector<int> a, b;
    a.push_back(0);
    b.push_back(1);

    auto one = [&] (int i) {
      if (are_connected({a.back()}, {i})) a.push_back(i);
      else if (are_connected({b.back()}, {i})) b.push_back(i);
      else {
        reverse(b.begin(), b.end());
        for(int &j : b) a.push_back(j);
        b = {i};
      }
    };

    auto two = [&] (int i) {
      if (are_connected({i}, {i + 1})) {
        if (are_connected({a.back()}, {i})) {
          a.push_back(i);
          a.push_back(i + 1);
        }
        else if (are_connected({b.back()}, {i})) {
          b.push_back(i);
          b.push_back(i + 1);
        }
        else {
          a = sum(a, rev(b));
          b = {i, i + 1};
        }
      }
      else {
        if (are_connected({a.back()}, {i})) {
          if (are_connected({b.back()}, {i + 1})) {
            a.push_back(i);
            b.push_back(i + 1);
          }
          else {
            a.push_back(i);
            a = sum(a, rev(b));
            b = {i + 1};
          }
        }
        else {
          if (are_connected({b.back()}, {i})) {
            a.push_back(i + 1);
            b.push_back(i);
          }
          else {
            a.push_back(i + 1);
            a = sum(a, rev(b));
            b = {i};
          }
        }
      }
    };

    for(int i = 2; i < n; i += 2) {
      if (i + 1 < n) two(i);
      else one(i);
    }

    if (a.size() > b.size()) swap(a, b);

    if (a.size() > 2 && !are_connected({a[0]}, {a.back()})) {
      if (are_connected({a[0]}, {b[0]})) return sum(rev(a), b);
      else return sum(a, b);
    }
    if (b.size() > 2 && !are_connected({b[0]}, {b.back()})) {
      if (are_connected({a[0]}, {b[0]})) return sum(rev(a), b);
      else return sum(b, a);
    }

    auto [x, y] = Find(a, b);
    if (x < 0) return b;
    vector<int> ans;
    for(int j = x + 1; j < a.size(); j++) ans.push_back(a[j]);
    for(int j = 0; j <= x; j++) ans.push_back(a[j]);
    for(int j = y; j < b.size(); j++) ans.push_back(b[j]);
    for(int j = 0; j < y; j++) ans.push_back(b[j]);
    return ans;
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::pair<int, int> Find(std::vector<int>, std::vector<int>)':
longesttrip.cpp:12:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   12 |     int mid = l + r >> 1;
      |               ~~^~~
longesttrip.cpp:22:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   22 |     int mid = l + r >> 1;
      |               ~~^~~
longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:120:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  120 |     for(int j = x + 1; j < a.size(); j++) ans.push_back(a[j]);
      |                        ~~^~~~~~~~~~
longesttrip.cpp:122:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  122 |     for(int j = y; j < b.size(); j++) ans.push_back(b[j]);
      |                    ~~^~~~~~~~~~

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