Submission #972530

#	Time	Username	Problem	Language	Result	Execution time	Memory
972530		MilosMilutinovic	Triangles (CEOI18_tri)	C++14	75 / 100	1049 ms	122104 KiB

tri

#include <bits/stdc++.h>
#include "trilib.h"
 
using namespace std;
 
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n = get_n();
  map<array<int, 3>, bool> mp;
  auto Ask = [&](int i, int j, int k) {
    if (mp.count({i, j, k})) {
      return mp[{i, j, k}];
    }
    mp[{i, j, k}] = is_clockwise(i, j, k);
    return mp[{i, j, k}];
  };
  vector<vector<int>> pts(2);
  for (int i = 3; i <= n; i++) {
    pts[!Ask(1, 2, i)].push_back(i);
  }
  pts[1].push_back(2);
  for (int it = 0; it < 2; it++) {
    sort(pts[it].begin(), pts[it].end(), [&](int i, int j) {
      if (i == j) {
        return false;
      }
      return !Ask(1, i, j);
    });
  }
  vector<int> v;
  for (int i : pts[1]) {
    v.push_back(i);
  }
  v.push_back(1);
  for (int i : pts[0]) {
    v.push_back(i);
  }
  vector<int> res;
  int bef = 0;
  for (int it = 0; it < 2; it++) {
    bef = (int) res.size();
    for (int i : v) {
      while (res.size() >= 2 && Ask(res.rbegin()[1], res.back(), i)) {
        res.pop_back();
      }
      res.push_back(i);
    }
  }
  cout << (int) res.size() - bef << endl;
  return 0;
}

• Subtask 1: 15 / 15
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 0 / 25