浮点数二分

## 浮点数二分

~~~c++
int test(int l,int r)
{
   double x;
   cin>>x;
   double l = 0,r = x;
    
   while(r - l<1e-6)
   {
      double mid = (l+r)/2;
       if(check(mid)) r = mid;
       else l = mid;
   }   
    cout<<l<<endl;
}