Submission #972521

#	Time	Username	Problem	Language	Result	Execution time	Memory
972521		MilosMilutinovic	Triangles (CEOI18_tri)	C++14	0 / 100	147 ms	262144 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();
  vector<vector<int>> pts(2);
  for (int i = 3; i <= n; i++) {
    pts[!is_clockwise(1, 2, i)].push_back(i);
  }
  pts[1].push_back(2);
  for (int it = 0; it < 2; it++) {
    int sz = (int) pts[it].size();
    vector<int> tmp(sz);
    function<void(int, int)> Solve = [&](int L, int R) {
      if (L == R) {
        return;
      }
      int mid = (L + R) >> 1;
      Solve(L, mid);
      Solve(mid + 1, R);
      for (int i = L; i <= R; i++) {
        tmp[i] = pts[it][i];
      }
      int pl = L, pr = mid + 1;
      int ptr = L;
      while (pl <= mid || pr <= R) {
        if (pl > mid) {
          tmp[ptr++] = pts[it][pr++];
        } else if (pr > R) {
          tmp[ptr++] = pts[it][pl++];
        } else if (is_clockwise(1, pts[it][pl], pts[it][pr])) {
          tmp[ptr++] = pts[it][pl++];
        } else {
          tmp[ptr++] = pts[it][pr++];
        }
      }
      for (int i = L; i <= R; i++) {
        pts[it][i] = tmp[i];
      }
    };
    Solve(0, sz - 1);
  }
  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 && is_clockwise(res.rbegin()[1], res.back(), i)) {
        res.pop_back();
      }
      res.push_back(i);
    }
  }
  cout << (int) res.size() - bef << endl;
  return 0;
}

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