1385.txt

北大ACM题目例程 详细的解答过程 程序实现 算法分析

#include"iostream.h"
#include"stdio.h"
#include"memory.h"

double x,y,x1,y1,xb,yb;
double area,x_sum,y_sum,temp;

int main()
{
	int t,n,i;
	cin>>t;
	while(t--)
	{
		cin>>n;
		cin>>x1>>y1;
		
		xb=x1,yb=y1;

		area=x_sum=y_sum=0;
		for(i=1;i<=n;i++)
		{
			if(i<n)cin>>x>>y;
			else x=xb,y=yb;

			temp=x*y1-y*x1;
			x_sum+=temp*(x+x1);
			y_sum+=temp*(y+y1);
			area+=temp;
			x1=x,y1=y;
		}

		printf("%.2lf %.2lf\n",(double)((long)(x_sum/area/3*100))/100,(double)(long)(y_sum/area/3*100)/100);
	}
	return 0;
}