省选专练（大水题）usaco2008feb-silver连线游戏

貌似x/y排个序

手动unique就好了

#include<bits/stdc++.h>
using namespace std;
const double eps=1e-16;
const double INF=1e16;
int cmp(double A){
	if(fabs(A)<eps)return 0;
	else return(A>0)?1:-1;
}
bool equal(double A,double B){
	return (cmp(A-B)==0);
}
struct Point{
	double x,y;
	double Ang;
	Point(double _x=0.0,double _y=0.0):x(_x),y(_y){}
	friend Point operator + (Point A,Point B){return Point(A.x+B.x,A.y+B.y);}
	friend Point operator - (Point A,Point B){return Point(A.x-B.x,A.y-B.y);}
	friend Point operator * (Point A,double k){return Point(A.x*k,A.y*k);}
	friend Point operator / (Point A,double k){return Point(A.x/k,A.y/k);}
	void ang(){if(x!=0)Ang=y/x;else Ang=-1.23456789;}
	void read(){scanf("%lf%lf",&x,&y);}
}p[4000];
typedef Point Vectors;
double Cross(Vectors A,Vectors B){
	return (A.x*B.y-A.y*B.x);
}
Vectors len[50000];
int vis[50000]={};
int n;
int top=0;
bool cmpV(Vectors A,Vectors B){
	return (cmp(A.Ang-B.Ang)<0);
}
int main(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		p[i].read(); 
	}
	for(int i=1;i<=n;i++){
		for(int j=i+1;j<=n;j++){
			len[++top]=p[i]-p[j];
			len[top].ang();
		}
	} 
	sort(len+1,len+1+top,cmpV);
	int ans=0;
	len[0].Ang=-0.123456789;
	for(int i=1;i<=top;i++){
		if(!equal(len[i].Ang,len[i-1].Ang)){
//			cout<<len[i].Ang<<len[i].x<<" "<<len[i].y<<'\n';
			ans++;
		}
	}
	/*for(int i=1;i<=top;i++){
		if(!vis[i]){
			for(int j=i+1;j<=top;j++){
				if(!vis[j]&&cmp(Cross(len[i],len[j]))==0)vis[j]=1;
			}
		}
	}*/ 
	/*int ans=0;
	for(int i=1;i<=top;i++){
		if(!vis[i]){
			ans++;
//			cout<<len[i].x/len[i].y<<'\n';
		}
	}*/ 
	cout<<ans;
}