FZU 2148: Moon Game 四边形的月亮

#include<cstdio>
#include<cmath>
using namespace std;

const double eps=1e-9;
const int N = 50;
struct point
{
int x, y;
} p
;

double cross(point a, point b, point c)
{
return a.x * b.y + c.x * a.y + b.x * c.y - c.x * b.y - a.x * c.y - b.x * a.y;
}

bool check(point a, point b, point c, point d)
{
if (fabs(fabs(cross(a, b, d))+fabs(cross(a, c, d))+fabs(cross(b, c, d))-fabs(cross(a, b, c)))<eps)
return true;
return false;
}

bool judge(point a, point b, point c, point d)
{
if (check(a, b, c, d)||check(a, b, d, c)||check(a, c, d, b)||(check(b, c, d, a)))
return false;
return true;
}

int main()
{
int t, n, cas=0;
scanf("%d", &t);
while(t--)
{
scanf("%d", &n);
for (int i = 0; i < n; ++i)
scanf("%d%d",&p[i].x,&p[i].y);
int ans = 0;
for (int i = 0; i < n; ++i)
for (int j = i + 1; j < n; ++j)
for (int k = j + 1; k < n; ++k)
for (int l = k + 1; l < n; ++l)
if (judge(p[i], p[j], p[k], p[l]))
ans++;
printf("Case %d: %d\n", ++cas, ans);
}
return 0;
}