hihoCoder #1040 （判断是否为矩形）

# include<iostream>
# include<cstdio>
# include<cmath>
# include<set>
# include<cstring>
# include<algorithm>
using namespace std;
# define LL long long

const double inf=1e20;
const double eps=1e-20;

struct Edge
{
LL x,y;
double k;
};
Edge e[4];
set<LL>s;

double getK(int i)
{
if(e[i].x==0) return inf;
return (double)e[i].y/(double)e[i].x;
}

bool ok(int i,int j)
{
return e[i].x*e[j].x+e[i].y*e[j].y==0ll;
}

bool judge()
{
if(s.size()!=4) return false;
int cnt1=0,cnt2=0;
for(int i=1;i<4;++i){
if(ok(0,i)) ++cnt1;
if(e[0].k==e[i].k) ++cnt2;
}
return cnt1==2&&cnt2==1;
}

int main()
{
int T;
scanf("%d",&T);
while(T--)
{
LL a,b,c,d;
s.clear();
for(int i=0;i<4;++i){
scanf("%lld%lld%lld%lld",&a,&b,&c,&d);
s.insert(a*100000ll+b);
s.insert(c*100000ll+d);
e[i].x=c-a;
e[i].y=d-b;
e[i].k=getK(i);
}
if(judge()) printf("YES\n");
else printf("NO\n");
}
return 0;
}