杭电2037 计算几何

计算几何入门题叉乘求面积

#include
#include
#include
using namespace std;
struct dian
{double x,y;}a[105];
int main()
{int i,j,k,m,n;
while(cin>>n&&n!=0)
{	for(i=0;i>a[i].x>>a[i].y;
double area=0.0;
  a[n].x=a[0].x;
  a[n].y=a[0].y;
        for(i=1;i<=n;++i)
            area+=a[i-1].x*a[i].y-a[i].x*a[i-1].y;
cout<