Submission #1403958

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
void _dbg(string){cout<<endl;}
template<class H,class... T> void _dbg(string s,H h,T... t){int l=s.find(',');cout<<s.substr(0,l)<<" = "<<h<<", ";_dbg(s.substr(l+1),t...);}
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 1120000000

using Point = complex<long>;
#define X real()
#define Y imag()
#define LE(n,m) ((n) < (m) + EPS)
#define GE(n,m) ((n) + EPS > (m))
#define EQ(n,m) (abs((n)-(m)) < EPS)

namespace std {
  bool operator<(const Point a, const Point b) {
    return a.X != b.X ? a.X < b.X : a.Y < b.Y;
  }
}

// 内積　dot(a,b) = |a||b|cosθ
long dot(Point a, Point b){
  return a.X*b.X + a.Y*b.Y;
}
// 外積　cross(a,b) = |a||b|sinθ
long cross(Point a, Point b){
  return a.X*b.Y - a.Y*b.X;
}


class AddableConvexHull {
public:
  set<Point> upperHull, lowerHull;
  AddableConvexHull(){}

  bool isCovered(set<Point> &hull, Point p){
    if(hull.size()==0) return false;
    if(hull.size()==1){
      Point q = *begin(hull);
      return q.X == p.X && q.Y >= p.Y;
    }
    // hull.size() >= 2
    auto l = begin(hull);
    auto r = --end(hull);
    if(p.X < l->X || p.X > r->X) return false;

    auto q1 = hull.upper_bound((Point){p.X, INF});
    if( q1==end(hull) ){
      return (--q1)->Y >= p.Y;
    }
    auto q2 = q1--; //dbg(*q1,*q2, q2==end(hull));
    // q1.x <= p.x < q2.x
    return cross(p - *q1, *q2 - *q1) >= 0;
  }

  bool inPolygon(Point p){
    bool bu = isCovered(upperHull, p);
    bool bl = isCovered(lowerHull, (Point){p.X, -p.Y});
    return bu==true && bl==true;
  }

  // only for upper hull
  void add(set<Point> &hull, Point p){
    if(hull.size()==0){
      hull.insert(p);
      return;
    }
    if(hull.size()==1){
      if(begin(hull)->X == p.X){
        Point q = *begin(hull);
        hull.clear();
        hull.insert(max(p,q));
      }
      else {
        hull.insert(p);
      }
      return;
    }
    // hull.size() >= 2

    if(isCovered(hull, p)) return;

    // left
    auto q1 = hull.upper_bound((Point){p.X, INF});
    if(q1 != begin(hull)){
      q1--;
      while(hull.size()>1 && q1!=begin(hull)){
        auto q2 = q1--; //dbg(*q1,*q2,cross(*q2 - p, *q1 - p));
        if( cross(*q2 - p, *q1 - p) > 0 ) break;
        hull.erase(q2);
      }
    }

    // right
    q1 = hull.lower_bound((Point){p.X, -INF});
    if(q1 != end(hull)){
      while(hull.size()>1 && q1 != --end(hull)){
        auto q2 = q1++; //dbg(*q1,*q2,cross(*q2 - p, *q1 - p));
        if( cross(*q1 - p, *q2 - p) > 0 ) break;
        hull.erase(q2);
      }
    }

    hull.insert(p);
  }

  void add(Point p){
    add(upperHull, p);
    add(lowerHull, (Point){p.X, -p.Y});
    // dbg(vector<Point>(all(upperHull)));
    // dbg(vector<Point>(all(lowerHull)));
  }
};

int main(){
  int n;
  cin>>n;

  AddableConvexHull hull;

  rep(i,n){
    string s;
    long x,y;
    cin>>s>>x>>y;
    if(s[0]=='M') {
      hull.add(Point{x,y});
    }
    else {
      if( hull.inPolygon(Point{x,y}) ) cout << "DANGER" << endl;
      else cout << "SAFE" << endl;
    }
  }

  return 0;
}

Submission Info

Judge Result