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