hdu 1115 Lifting the Stone【求多边形重心】

​​http://acm.hdu.edu.cn/showproblem.php?pid=1115​​

代码：

#include <iostream>
#include <set>
#include <string>
#include <cstdio>
#include <string.h>
#include <algorithm>
#include <vector>

using namespace std;

double x0, y0, x1, y1, x2, y2;
double s0, s1, s2;
double x, y;

int n;

int main()
{
    int t;
    scanf("%d",&t);

    while (t--)
    {
        scanf ("%d",&n);
        s0 = s1 = s2 = 0;
        cin >> x0 >> y0 >> x1 >> y1;
        for (int i = 2;i < n;i++)
        {
            cin >> x2 >> y2;
            x = (x0 + x1 + x2);
            y = (y0 + y1 + y2);

            double tmp = (x0*y1 + x1 * y2 + x2*y0 - x1*y0 - x2 * y1 - x0*y2);

            s0 += tmp;
            s1 += x*tmp;
            s2 += y*tmp;

            x1 = x2;
            y1 = y2;

        }
        //cout<<s0<<endl;
        if (s0 == 0)
            printf("0.00 0.00\n");
        else
            printf("%.2lf %.2lf\n", s1 / s0 / 3, s2 / s0 / 3);
    }
    return 0;
}