My code

… was written in C++ and can be compiled with G++, Clang++, Visual C++. You can download it, as well as the input data, too. Or just jump to my GitHub repository.

The code contains #ifdefs to switch between the original problem and the Hackerrank version.
Enable #ifdef ORIGINAL to produce the result for the original problem (default setting for most problems).

       
#include <iostream>
       
 
       
//#define ORIGINAL

       
 
       
// compute dot-product

       
double dot(double x, double y, double x1, double y1, double x2, double y2)
       
{
       
  return (y2 - y1)*(x - x1) + (x1 - x2)*(y - y1);
       
}
       
 
       
// return true if point (x,y) is inside the triangle (x1,y1),(x2,y2),(x3,y3)
       
// uses dot-product

       
bool isInside(double x, double y, double x1, double y1, double x2, double y2, double x3, double y3)
       
{
       
  bool sign1 = dot(x,y, x1,y1, x2,y2) >= 0;
       
  bool sign2 = dot(x,y, x2,y2, x3,y3) >= 0;
       
  bool sign3 = dot(x,y, x3,y3, x1,y1) >= 0;
       
 
       
  return (sign1 == sign2) && (sign2 == sign3);
       
}
       
 
       
// same as above but based on barycentric coordinates

       
bool isInside2(double x, double y, double x1, double y1, double x2, double y2, double x3, double y3)
       
{
       
  double denominator = (y2 - y3)*(x1 - x3) + (x3 - x2)*(y1 - y3);
       
 
       
  double a = ((y2 - y3)*(x - x3) + (x3 - x2)*(y - y3)) / denominator;
       
  double b = ((y3 - y1)*(x - x3) + (x1 - x3)*(y - y3)) / denominator;
       
  double c = 1 - a - b;
       
 
       
  return 0 <= a && a <= 1 &&
       
         0 <= b && b <= 1 &&
       
         0 <= c && c <= 1;
       
}
       
 
       
int main()
       
{
       
  // number of triangles where the origin is inside
       
  unsigned int numInside = 0;
       
 
       
  unsigned int tests = 1000;
       
#ifndef ORIGINAL
       
  std::cin >> tests;
       
#endif
       
 
       
  while (tests--)
       
  {
       
    int x1,y1,x2,y2,x3,y3;
       
 
       
#ifdef ORIGINAL
       
    // numbers in CSV format
       
    char comma;
       
    std::cin >> x1 >> comma >> y1 >> comma >> x2 >> comma >> y2 >> comma >> x3 >> comma >> y3;
       
#else
       
    // numbers separated by spaces
       
    std::cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
       
#endif
       
 
       
    // both algorithms return the same results
       
    if (isInside(0,0, x1,y1, x2,y2, x3,y3))
       
      numInside++;
       
    //if (isInside2(0,0, x1,y1, x2,y2, x3,y3))
       
    //  numInside++;
       
  }
       
 
       
  std::cout << numInside << std::endl;
       
  return 0;
       
}

This solution contains 13 empty lines, 11 comments and 6 preprocessor commands.