Submission #498602

#	Time	Username	Problem	Language	Result	Execution time	Memory
498602		codebuster_10	Roads (CEOI20_roads)	C++17	100 / 100	264 ms	20016 KiB

roads

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

#define int int64_t //be careful about this 

#define pr pair
#define ar array
#define f first
#define s second
#define vt vector
#define pb push_back
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound

#define SZ(x) ((int)(x).size())
#define all(a) (a).begin(),(a).end()
#define allr(a) (a).rbegin(),(a).rend()
#define mem(a,b) memset(a, b, sizeof(a))

template<class A> void rd(vt<A>& v);
template<class T> void rd(T& x){ cin >> x;}
template<class H, class... T> void rd(H& h, T&... t) { rd(h); rd(t...);}
template<class A> void rd(vt<A>& x) { for(auto& a : x) rd(a);}

template<class T> bool ckmin(T& a, const T b) { return b < a ? a = b, 1 : 0;}
template<class T> bool ckmax(T& a, const T b) { return a < b ? a = b, 1 : 0;}

template<typename T>
void __p(T a) {
  cout<<a; 
}
template<typename T, typename F>
void __p(pair<T, F> a) {
  cout<<"{";
  __p(a.first);
  cout<<",";
  __p(a.second);
  cout<<"}\n"; 
}
template<typename T>
void __p(std::vector<T> a) {
  cout<<"{";
  for(auto it=a.begin(); it<a.end(); it++)
    __p(*it),cout<<",}\n"[it+1==a.end()]; 
}
template<typename T, typename ...Arg>
void __p(T a1, Arg ...a) {
  __p(a1);
  __p(a...);
}
template<typename Arg1>
void __f(const char *name, Arg1 &&arg1) {
  cout<<name<<" : ";
  __p(arg1);
  cout<<endl;
}
template<typename Arg1, typename ... Args>
void __f(const char *names, Arg1 &&arg1, Args &&... args) {
  int bracket=0,i=0;
  for(;; i++)
    if(names[i]==','&&bracket==0)
      break;
    else if(names[i]=='(')
      bracket++;
    else if(names[i]==')')
      bracket--;
  const char *comma=names+i;
  cout.write(names,comma-names)<<" : ";
  __p(arg1);
  cout<<" | ";
  __f(comma+1,args...);
}
#define trace(...) cout<<"Line:"<<__LINE__<<"  ", __f(#__VA_ARGS__, __VA_ARGS__)


void setIO(string s = "") {
  ios_base::sync_with_stdio(0); cin.tie(0); 
	cout.precision(20);	cout << fixed;
  if(SZ(s)){
  	freopen((s+".in").c_str(),"r",stdin);
  	freopen((s+".out").c_str(),"w",stdout);
  }
}


/*/--------------------------------------------------look below-----------------------------------------------------------------------------------/*/



























struct point{
	int x,y,id;
};

struct line{
	point s,e;
};

bool operator<(const point& a,const point& b){
	return a.x==b.x?a.y<b.y:a.x<b.x;
}

int curr_x;

bool operator<(const line& a,const line& b){
	double yA, yB;
  if(a.s.x == a.e.x) yA = a.s.y;
  else{
    double m = double(a.e.y - a.s.y) / (a.e.x - a.s.x);
    double c = a.s.y - m * a.s.x;
    yA = m * curr_x + c;
  }
  if(b.s.x == b.e.x) yB = b.s.y;
  else {
    double m = double(b.e.y - b.s.y) / (b.e.x - b.s.x);
    double c = b.s.y - m * b.s.x;
    yB = m * curr_x + c;
  }
  return yA < yB;
}



bool operator==(const line& a,const line& b){
    return a.s.id == b.s.id;
}

signed main(){
  setIO();
  int n;
  rd(n);
  vt<line> s(n);
  vt<point> Rmost(n+1);
  vt<point> events;
  for(int i = 0; i < n; ++i){
  	rd(s[i].s.x,s[i].s.y,s[i].e.x,s[i].e.y);
  	if(s[i].e < s[i].s)
  		swap(s[i].s,s[i].e);
  	s[i].s.id=s[i].e.id=i;
  	events.pb(s[i].s);
  	events.pb(s[i].e);
  }
  sort(all(events));
  set<line> active;
  point ninf = {INT_MIN, INT_MAX, n}, inf = {INT_MAX, INT_MAX, n};
  active.insert({ninf, inf});
  Rmost[n] = {0, 0, -1};

  for(auto i : events){
  	curr_x = i.x;
  	if(active.find(s[i.id]) != active.end()){
  		active.erase(s[i.id]);
  		auto nxt = active.lower_bound(s[i.id]);
      Rmost[nxt->s.id] = i;
  	}else{
  		auto nxt = active.lower_bound(s[i.id]);
  		if(Rmost[nxt->s.id].id != -1){
        cout << Rmost[nxt->s.id].x << " " << Rmost[nxt->s.id].y << " " << i.x << " " << i.y << '\n';
      }
      Rmost[i.id] = Rmost[nxt->s.id] = i;
      active.insert(s[i.id]);
  	}
  }
  
  return 0;
}







// tips to avoid bugs.

/*
	* be careful of whats happening you dont want a continue statement to miss imp line of code.
	* be careful when to update what since it might be needed in next segment of code.
	* dont get stuck on one idea.
  * dont use too much space bar so that code is written quickly as possible.
*/

Compilation message (stderr)

roads.cpp: In function 'void setIO(std::string)':
roads.cpp:81:11: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |    freopen((s+".in").c_str(),"r",stdin);
      |    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
roads.cpp:82:11: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   82 |    freopen((s+".out").c_str(),"w",stdout);
      |    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 0
• Subtask 2: 15 / 15
• Subtask 3: 15 / 15
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 40 / 40