SPOJ : PIR Solution

Question:PIR - Pyramids
Explaination 
Use the formula  
 
Heron-type formula for the volume of a tetrahedron
If U, V, W, u, v, w are lengths of edges of the tetrahedron (first three form a triangle; u opposite to U and so on), then
                                                             
    volume=\/(-a+b+c+d)*(a-b+c+d)*(a+b-c+d)*(a+b+c-d)  
                            192*u*v*w 
where                           
a=\/xYZ  b=\/yZX    c=\/zXY  d=\/xyz 
X=(w-U+v)*(U+v+w) 
x=(U-v+w)*(v-w+U)
Y=(u-V+w)*(V+w+u)
y=(V-w+u)*(w-u+V)
Z=(v-W+u)*(W+u+v)
z=(W-u+v)*(u-v+W) 

${\displaystyle {\begin{aligned}a&={\sqrt {xYZ}}\\b&={\sqrt {yZX}}\\c&={\sqrt {zXY}}\\d&={\sqrt {xyz}}\\X&=(w-U+v)\,(U+v+w)\\x&=(U-v+w)\,(v-w+U)\\Y&=(u-V+w)\,(V+w+u)\\y&=(V-w+u)\,(w-u+V)\\Z&=(v-W+u)\,(W+u+v)\\z&=(W-u+v)\,(u-v+W).\end{aligned}}}$

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<iostream>
#include<math.h>
#define LL long long
#define mx 10010
using namespace std;
int main()
{
    double u,v,w,U,V,W;
    int t=0;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf%lf%lf%lf%lf%lf",&u,&v,&w,&W,&V,&U);
        double a,b,c,d,x,y,z,X,Y,Z;
        X=(w-U+v)*(U+v+w);
        x=(U-v+w)*(v-w+U);
        Y=(u-V+w)*(V+w+u);
        y=(V-w+u)*(w-u+V);
        Z=(v-W+u)*(W+u+v);
        z=(W-u+v)*(u-v+W);
        a=sqrt(x*Y*Z);
        b=sqrt(y*Z*X);
        c=sqrt(z*X*Y);
        d=sqrt(x*y*z);
        double vol=(b+c+d-a)*(a-b+c+d)*(a+b-c+d)*(a+b+c-d);
        vol=sqrt(vol)/(192*u*v*w);
        printf("%.4lf\n",vol);
    }
    return 0;
}