版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/a17865569022/article/details/81913105
#include<bits/stdc++.h>
using namespace std;
struct node
{
double x;
double y;
}p[105];
int main()
{
int t;scanf("%d",&t);
while(t--)
{
int n;scanf("%d",&n);
for(int i=0;i<n;i++)
scanf("%lf %lf",&p[i].x,&p[i].y);
double sum=0;
for(int i=1;i<n-2;i++)
{
double temp1,temp2;
temp1=min(p[i].y,p[i+1].y)*fabs(p[i].x-p[i+1].x);
temp2=fabs(p[i].y-p[i+1].y)*fabs(p[i].x-p[i+1].x)/2;
sum+=(temp1+temp2);
}
double s1=(p[1].x-p[0].x)*p[1].y/2;
double s2=(p[n-1].x-p[n-2].x)*p[n-2].y/2;
sum+=(s1+s2);
printf("%.6lf\n",sum);
}
return 0;
}