poj 1385(多边形的重心)

求多边形的重心。

#include<stdio.h>

struct POINT
{
	double x,y;
}point[1000002];


POINT bcenter(POINT pnt[], int n){
	POINT p, s;
	double tp, area = 0, tpx = 0, tpy = 0;
	p.x = pnt[0].x; p.y = pnt[0].y;
	for (int i = 1; i <= n; ++i) { // point: 0 ~ n-1
		s.x = pnt[(i==n) ? 0 : i].x;
		s.y = pnt[(i == n) ? 0 : i].y;
		tp = (p.x * s.y - s.x * p.y);
		area += tp / 2;
		tpx += (p.x + s.x) * tp;
		tpy += (p.y + s.y) * tp;
		p.x = s.x; p.y = s.y;
	}
	s.x = tpx / (6 * area); s.y = tpy / (6 * area);
	return s;
}
int main()
{
	int t,n,i;
	POINT center;
	scanf("%d",&t);
	
	while(t--)
	{
		scanf("%d",&n);
		
		for(i=0;i<n;i++)
			scanf("%lf%lf",&point[i].x,&point[i].y);
		center=bcenter(point,n);
		printf("%.2lf %.2lf\n",center.x,center.y);
		
	}
	return 0;
}