Submission #954947

#	Time	Username	Problem	Language	Result	Execution time	Memory
954947		hyakup	Triangles (CEOI18_tri)	C++17	100 / 100	28 ms	2872 KiB

tri

#include <bits/stdc++.h>
#include "trilib.h"
#include <random>
using namespace std;

void ordena( vector<int>& v, vector<int>& resp ){
  if( v.size() == 1 ) return;
  vector<int> l, r;
  l.push_back(v[0]); r.push_back(v[0]);
  for( int i = 2; i < v.size(); i++ ){
    if( is_clockwise( v[0], v[1], v[i] ) ) r.push_back(v[i]);
    else l.push_back(v[i]);
  }
  ordena( l, resp ); resp.push_back(v[1]); ordena( r, resp );
}

int main(){
  mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
  int n = get_n();
  vector<int> v, resp, marc(n + 1, -1);
  for( int i = 1; i <= n; i++ ) v.push_back(i);
  shuffle( v.begin(), v.end(), rng );
  resp.push_back(v[0]); ordena(v, resp);
  for( int i = 0; i < n; i++ ) resp.push_back(resp[i]);

  vector<int> hull;
  for( int cur : resp ){
    while( hull.size() >= 2 && !is_clockwise( hull[hull.size() - 2], hull.back(), cur ) ) hull.pop_back();
    hull.push_back(cur);
  }

  for( int i = 0; i < hull.size() - 1; i++ ){
    if( marc[hull[i]] == -1 ){ marc[hull[i]] = i; continue; }
    give_answer(i - marc[hull[i]]); break;
  }
}

Compilation message (stderr)

tri.cpp: In function 'void ordena(std::vector<int>&, std::vector<int>&)':
tri.cpp:10:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |   for( int i = 2; i < v.size(); i++ ){
      |                   ~~^~~~~~~~~~
tri.cpp: In function 'int main()':
tri.cpp:32:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |   for( int i = 0; i < hull.size() - 1; i++ ){
      |                   ~~^~~~~~~~~~~~~~~~~

• Subtask 1: 15 / 15
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 25 / 25