Pass Triangle on Codeeval

pass_triangle.cpp

//Help came from Steven A. Dunn's code

#include <fstream>
#include <iostream>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;

void sum_calc(string, vector<long>&);

int main(int argc, char* argv[])
{
  ifstream file(argv[1]);
  string line;

  if (file)
  {
    stack<string> lineStack;
    while (getline(file, line))
    {
    	lineStack.push(line);
    	
    }
      

    vector<long> sums; // used by calculate sums function
    while (!lineStack.empty())
    {
      string line = lineStack.top();
      sum_calc(line, sums); //line = input string and sums is self-explanatory
      lineStack.pop();
    }

    cout << sums[0] << endl;

    file.close();
  }
  return 0;
}

void sum_calc(string line, vector<long>& runningSums) // reference type vector<long>& should be faster
/* Begins from the base of triangle and works up to apex */
{
  vector<long> numbers; // holds the line (string) as integers
  istringstream iss(line);
  
  long string; // takes the integer conversion
  while (iss >> string) // converting input strings (line) to integers here
    numbers.push_back(string);

  if (runningSums.size() == 0)
  {
  	/* This is the base of the triangle */
    runningSums = numbers; // places numbers into sums vector in main

    return; // break out of function for this line
  }

  vector<long> newSums; // create temp vector to hold progress before transference to runningSums
  for (int i = 0; i < runningSums.size() - 1; ++i)
  {
    long maxNum = 0;
    
    /* runningSums current is greater than the next value in line */
    maxNum = (runningSums[i] > runningSums[i+1]) ? runningSums[i] : runningSums[i+1];
    

    //DP adding previous result to new result
    newSums.push_back(maxNum + numbers[i]); 
    
  }

  runningSums = newSums;  
  return;
}