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>
       
#include <vector>
       
#include <algorithm>
       
 
       
int main()
       
{
       
  unsigned int tests = 1;
       
 
       
//#define ORIGINAL

       
#ifndef ORIGINAL
       
  std::cin >> tests;
       
#endif
       
 
       
  while (tests--)
       
  {
       
    unsigned int numRows = 15;
       
#ifndef ORIGINAL
       
    std::cin >> numRows;
       
#endif
       
 
       
    // process input row-by-row
       
    // each time a number is read we add it to the two numbers above it
       
    // choose the bigger sum and store it
       
    // if all rows are finished, find the largest number in the last row
       
 
       
    // read first line, just one number
       
    std::vector<unsigned int> last(1);
       
    std::cin >> last[0];
       
 
       
    // read the remaining lines
       
    for (unsigned int row = 1; row < numRows; row++)
       
    {
       
      // prepare array for new row
       
      unsigned int numElements = row + 1;
       
      std::vector<unsigned int> current;
       
 
       
      // read all numbers of current row
       
      for (unsigned int column = 0; column < numElements; column++)
       
      {
       
        unsigned int x;
       
        std::cin >> x;
       
 
       
        // find sum of elements in row above (going a half step to the left)
       
        unsigned int leftParent = 0;
       
        // only if left  parent is available
       
        if (column > 0)
       
          leftParent = last[column - 1];
       
 
       
        // find sum of elements in row above (going a half step to the right)
       
        unsigned int rightParent = 0;
       
        // only if right parent is available
       
        if (column < last.size())
       
          rightParent = last[column];
       
 
       
        // add larger parent to current input
       
        unsigned int sum = x + std::max(leftParent, rightParent);
       
        // and store this sum
       
        current.push_back(sum);
       
      }
       
 
       
      // row is finished, it become the "parent" row
       
      last = current;
       
    }
       
 
       
    // find largest sum in final row
       
    std::cout << *std::max_element(last.begin(), last.end()) << std::endl;
       
  }
       
 
       
  return 0;
       
}

This solution contains 13 empty lines, 17 comments and 7 preprocessor commands.