OJ-Problems-Source/HDOJ/1115_autoAC.cpp

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2016-08-13 10:51:15 +08:00
#include<stdio.h>
#include<math.h>
struct p{
double x,y;
};
double cross(p a,p b,p c){
return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);
}
int main(){
int t;
scanf("%d",&t);
while(t--){
int n;
p p1,p2,tp;
double res=0,s,tx=0,ty=0;
scanf("%d",&n);
scanf("%lf%lf%lf%lf",&p1.x,&p1.y,&p2.x,&p2.y);
for(int i=3;i<=n;++i){
scanf("%lf%lf",&tp.x,&tp.y);
s=cross(p1,p2,tp);
res+=s;
tx+=(p1.x+p2.x+tp.x)*s;
ty+=(p1.y+p2.y+tp.y)*s;
p2.x=tp.x;p2.y=tp.y;
}
printf("%.2lf %.2lf\n",tx/(3*res),ty/(3*res));
}
return 0;
}