hdu 1115 Lifting the Stone 多边形的重心

 

#include<iostream>
#include<cmath>
using namespace std;
struct point{
double x,y;
point (double xx=0,double yy=0){
x=xx; y=yy;
}
double operator *(point b){
return x*b.y-y*b.x;
}
}p[1000001];
int main()
{
int T,N,i;
scanf("%d",&T);
while(T--)
{
scanf("%d",&N);
for(i=0;i<N;i++)
scanf("%lf%lf",&p[i].x,&p[i].y);
p[N].x=p[0].x; p[N].y=p[0].y;
double area=0;
point re;
for(i=0;i<N;i++)
{
area+=p[i]*p[i+1];
re.x+=(p[i].x + p[i+1].x)* (p[i]*p[i+1]);
re.y+=(p[i].y + p[i+1].y)* (p[i]*p[i+1]);
}
area/=2;
re.x /= 6*area;
re.y /= 6*area;
printf("%.2lf %.2lf\n",re.x,re.y);
}
return 0;
}

 

转载于:https://www.cnblogs.com/DreamUp/archive/2010/08/28/1811431.html