How to reverse the order of a input file using C++?

Question

I need to reverse the order of the file and outputted into another file. For example, the

input:

hello
this is a testing file again
just    so    much  fun

Expected output:

just    so    much  fun
this is a testing file again 
hello

This is my current code, it printed to where it reverses the order of the lines but also the order of the characters of each word.

Current:

nuf  hcum    os    tsuj
 niaga elif gnitset a si siht
olleh

int print_rev(string filename, char c){
  ifstream inStream (filename);
  ofstream outStream;
  inStream.seekg(0,inStream.end);
  int size = inStream.tellg();
  outStream.open("output.txt");

  for (int j=1; j<=size; j++){ 
    inStream.seekg(-j, ios::end);
    c=inStream.get();
    outStream << c;
  }

  inStream.close();
  outStream.close();
  return 0;
}

Did you mean the expected output is "fun much so just again file testing a is this hello" ? — Aryan Mediratta, Feb 21 '19 at 01:52
The question needs format editing to better show the line-by-line nature of the file contents — Phil M, Feb 21 '19 at 01:55
Why are `text` and `c` passed in to the function? One isn't used at all, and the other is better served just being a local. — Phil M, Feb 21 '19 at 01:58
What is your design? *How* did you expect your code to do what you wanted? — Beta, Feb 21 '19 at 02:02
This code is meant to be a function that will be used by the main code — Kait26, Feb 21 '19 at 02:06
This https://stackoverflow.com/questions/10813930/read-a-file-backwards may be what you're looking for. — Michael Surette, Feb 21 '19 at 03:17

score 0 · Answer 1 · answered Feb 21 '19 at 03:36

You're reversing the whole file, character by character. What you want to do is read in each line separately, and then reverse the line order.

A stack of lines seems like a good choice for this :

int printRev(string filename)
{
    stack<string> lines;
    ifstream in(filename);
    string line;
    while (getline(in, line))
    {
        lines.push(line);
    }
    ofstream out("output.txt");
    while (!lines.empty())
    {
        out << lines.top() << endl;
        lines.pop();
    }
    return 0;
}

How to reverse the order of a input file using C++?

1 Answers1