Submission #226360

#	Time	Username	Problem	Language	Result	Execution time	Memory
226360		Bruteforceman	Printed Circuit Board (CEOI12_circuit)	C++11	35 / 100	1096 ms	5368 KiB

circuit

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 5;
int n;
struct point {
  long long x, y;
  point () {}
  point (long long x, long long y) : x(x), y(y) {}
  point operator + (point p) const {
    return point(x + p.x, y + p.y);
  }
  point operator - (point p) const {
    return point(x - p.x, y - p.y);
  }
} a[maxn];
int ord[maxn];

long long cross(point p, point q) { return p.x * q.y - p.y * q.x; }
long long dot(point p, point q) { return p.x * q.x + p.y * q.y; }
bool inSegment(point a, point b, point c) {
  return cross(c - a, b - a) == 0 && 
    dot(a - b, a - b) >= max(dot(a - c, a - c),  dot(c - b, c - b));
}
int side(point a, point b, point c) { 
  long long x = cross(b - a, c - a);
  if(x > 0) return 1;
  else if (x < 0) return -1;
  else return 0;
}
bool intersect(point a, point b, point c, point d) {
  if(side(a, b, c) * side(a, b, d) == -1 &&
      side(c, d, a) * side(c, d, b) == -1) return true;
  for(auto i : {c, d}) if(inSegment(a, b, i)) return true;
  for(auto i : {a, b}) if(inSegment(c, d, i)) return true;
  return false;
}
double sect(point a, point b, point c) {
  point f = b - a;
  return double(c.x * cross(a, f)) / cross(c, f);
}
int main() { 
  cin >> n;
  for(int i = 0; i < n; i++) {
    cin >> a[i].x >> a[i].y;
    ord[i] = i;
  } 
  auto cmp = [&] (int i, int j) {
      return cross(a[i], a[j]) > 0 || 
        (cross(a[i], a[j]) == 0 && dot(a[i], a[i]) < dot(a[j], a[j])); 
  };
  sort(ord, ord + n, cmp); 

  vector <int> res;
  set <pair <int, int>> can;
  int cur = 0;
  while(cur < n) {
    int x = ord[cur];
    for(int i : {-1, 1}) {
      int y = (x + i + n) % n;
      if(cross(a[x], a[y]) < 0) {
        can.erase(make_pair(y, x));
       // cout << "erase " << y+1 << " " << x+1 << endl;
      }
    }
    if(cur == 0 || cross(a[ord[cur - 1]], a[ord[cur]]) != 0) {
      bool bad = false;
      double ox = INT_MAX;
      for(auto i : can) {
        ox = min(ox, sect(a[i.first], a[i.second], a[x])); 
      }
      if(a[x].x <= ox) res.emplace_back(x+1);
     // cout << "check " << x << endl;
    }
    for(int i : {-1, 1}) {
      int y = (x + i + n) % n;
      if(cross(a[x], a[y]) > 0) {
        can.insert(make_pair(x, y));
      //  cout << "insert " << x+1 << " " << y+1 << endl;
      }
    }
    cur++;
  }
  sort(res.begin(), res.end());
  cout << res.size() << endl;
  for(auto i : res) cout << i << " ";
  cout << endl;
  return 0;
}

Compilation message (stderr)

circuit.cpp: In function 'int main()':
circuit.cpp:66:12: warning: unused variable 'bad' [-Wunused-variable]
       bool bad = false;
            ^~~

• Subtask 1: 35 / 100