bzoj1173: [Balkan2007]Point

#include<cstdio>
#include<algorithm>
inline int gcd(int x,int y){
    for(int z;y;z=x,x=y,y=z%y);
    return x;
}
int n;
struct pos{
    int x,y,z;
    void fix(){
        int g=gcd(gcd(x,y),z);
        x/=g;y/=g;z/=g;
        if(x!=0?x<0:y!=0?y<0:z<0)x=-x,y=-y,z=-z;
    }
}ps[1007];
bool operator==(const pos&a,const pos&b){return a.x==b.x&&a.y==b.y&&a.z==b.z;}
bool operator<(const pos&a,const pos&b){return a.x!=b.x?a.x<b.x:a.y!=b.y?a.y<b.y:a.z<b.z;}
pos operator-(pos a,pos b){return (pos){a.x-b.x,a.y-b.y,a.z-b.z};}
struct line{
    int a,b;
    pos v;
}as[1007*555];
bool operator<(const line&a,const line&b){return a.v<b.v;}
int ap=0,ans=0;
int es[1000007],enx[1000007],e0[1007],ep=2,ds[1007],dp=0,T,tk[1007];
int dfs(int w){
    int c=1;
    tk[w]=T;
    for(int i=e0[w];i;i=enx[i]){
        int u=es[i];
        if(tk[u]!=T)c+=dfs(u);
    }
    return c;
}
void adde(int a,int b){
    if(!e0[a])ds[dp++]=a;
    if(!e0[b])ds[dp++]=b;
    es[ep]=b;enx[ep]=e0[a];e0[a]=ep++;
    es[ep]=a;enx[ep]=e0[b];e0[b]=ep++;
}
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;++i)scanf("%d%d%d",&ps[i].x,&ps[i].y,&ps[i].z);
    for(int i=1;i<=n;++i){
        for(int j=1;j<i;++j){
            (as[ap++]=(line){i,j,ps[i]-ps[j]}).v.fix();
        }
    }
    std::sort(as,as+ap);
    for(int i=0,j=0;i<ap;){
        for(;j<ap&&as[i].v==as[j].v;++j);
        for(++T;i<j;++i)adde(as[i].a,as[i].b);
        for(int k=0;k<dp;++k)if(dfs(ds[k])>=3)++ans;
        while(dp)e0[ds[--dp]]=0;ep=2;
    }
    printf("%d\n",ans);
    return 0;
}