OJ-Problems-Source/HDOJ/2298_autoAC.cpp

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#include<stdio.h>
#include<cmath>
double x,y,v;
const double g=9.8;
double f(double a)
{
return x*tan(a)-x*x*g/(2*v*v*cos(a)*cos(a));
}
double sanf(double bottom,double top)
{
double rightthir,leftthir;
while(top-bottom>1e-9)
{
rightthir=(bottom+top*2)/3;
leftthir=(bottom*2+top)/3;
if(f(rightthir)>f(leftthir))
{
bottom=leftthir+1e-10;
}
else
{
top=rightthir-1e-10;
}
}
return (top+bottom)/2;
}
double erfen(double bottom,double top)
{
double mid;
while(top-bottom>1e-9)
{
mid=(top+bottom)/2;
if(f(mid)>y)
{
top=mid-1e-10;
}
else
{
bottom=mid+1e-10;
}
}
return (bottom+top)/2;
}
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
scanf("%lf%lf%lf",&x,&y,&v);
double max=sanf(0,3.1415926535897932384626433832795/2.0);
if(f(max)<y)
{
printf("-1\n");
}
else
{
printf("%.6lf\n",erfen(0,max));
}
}
}