UVA - 10347 - Medians（由三中线求三角形面积）

AC代码：

 #include<cstdio>
 #include<cmath>
 #include<algorithm>
 #include<iostream>
 #include<cstring>
 using namespace std;
 typedef long long ll;
 const double eps = 1e-;
 int sgn(double x)
 {
     if(fabs(x) < eps) return ;
     else return x <  ? - : ;
 }
 int main()
 {
     double a, b ,c;
     while(~scanf("%lf %lf %lf",&a,&b,&c))
     {
         if(a!= && b !=  && c !=  && sgn(a + b - c) > && sgn( a + c - b ) >  &&sgn( b + c - a) > )
         {
             double p =a + b + c;
             double Elem1 = p -*a;
             double Elem2 = p -*b;
             double Elem3 = p -*c;
             double S=sqrt(p *Elem1*Elem2*Elem3);
             S/=;
             printf("%.3f\n",S);
         }
         else
            printf("-1.000\n");
     }
     return ;
 }