Formatting files - C++ - c++

Question

I have hit a brick wall trying to format one of my files. I have a file that I have formatted to look like this:
0 1 2 3 4 5
0.047224 0.184679 -0.039316 -0.008939 -0.042705 -0.014458
-0.032791 -0.039254 0.075326 -0.000667 -0.002406 -0.010696
-0.020048 -0.008680 -0.000918 0.302428 -0.127547 -0.049475
...
6 7 8 9 10 11
[numbers as above]
12 13 14 15 16 17
[numbers as above]
...
Each block of numbers has exactly the same number of lines. What I am trying to do is basically move every block (including the headers) to the right of the first block so in the end my output file would look like this:
0 1 2 3 4 5 6 7 8 9 10 11 ...
0.047224 0.184679 -0.039316 -0.008939 -0.042705 -0.014458 [numbers] ...
-0.032791 -0.039254 0.075326 -0.000667 -0.002406 -0.010696 [numbers] ...
-0.020048 -0.008680 -0.000918 0.302428 -0.127547 -0.049475 [numbers] ...
...
So in the end I should basically get a nxn matrix (only considering the numbers). I already have a python/bash hybrid script that can format this file
exactly like this BUT I've switched the running of my code from Linux to Windows and hence cannot use the bash part of the script anymore (since my code has to be compliant will all versions of Windows). To be honest I have no idea how to do it so any help would be appreciated!
Here's what I tried until now (it's completely wrong I know but maybe I can build on it...):
void finalFormatFile()
{
ifstream finalFormat;
ofstream finalFile;
string fileLine = "";
stringstream newLine;
finalFormat.open("xxx.txt");
finalFile.open("yyy.txt");
int countLines = 0;
while (!finalFormat.eof())
{
countLines++;
if (countLines % (nAtoms*3) == 0)
{
getline(finalFormat, fileLine);
newLine << fileLine;
finalFile << newLine.str() << endl;
}
else getline(finalFormat, fileLine);
}
finalFormat.close();
finalFile.close();
}

Answer 1

For such a task, I would do it the simple way. As we already know the number of lines and we know the pattern, I would simply keep a vector of strings (one entry per line of the final file) that I would update as I'm parsing the input file. Once it's done, I would iterate through my strings to print them into the final file. Here is a code that's doing it :
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
int main(int argc, char * argv[])
{
int n = 6; // n = 3 * nAtoms
std::ifstream in("test.txt");
std::ofstream out("test_out.txt");
std::vector<std::string> lines(n + 1);
std::string line("");
int cnt = 0;
// Reading the input file
while(getline(in, line))
{
lines[cnt] = lines[cnt] + " " + line;
cnt = (cnt + 1) % (n + 1);
}
// Writing the output file
for(unsigned int i = 0; i < lines.size(); i ++)
{
out << lines[i] << std::endl;
}
in.close();
out.close();
return 0;
}
Note that, depending of the structure of your input/ouput files, you might want to adjust the line lines[cnt] = lines[cnt] + " " + line in order to separate the columns with the right delimiter.