/* sort.cpp - Matt Mahoney, mmahoney@cs.fit.edu

This program sorts lines of text in lexicographical (ASCII code)
order to standard output from the file name given on the command line,
or from standard input if no file name is specified, for instance:

  sort input.txt >output.txt
or
  sort <input.txt >output.txt

In lexicographcial order, the lines of text are printed such that
the ASCII codes of the first nonmatching characters of consecutive lines
are in ascending order.  If one line is a prefix of the other, then
the shorter line is printed first.  In ASCII order, spaces precede
digits (0-9), which precede uppercase letters (A-Z), which precede
lowercase (a-z).  For instance:

input.txt (lines may be in any order)
  9
  10
  cat and dog.
  cat
  cats.
   cat
  Cat
  car

output.txt (sorted)
   cat
  10
  9
  Cat
  car
  cat
  cat and dog.
  cats.

If a file name argument is supplied and the file does not exist,
sort prints an error message to standard error output (not redirected).
*/

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

// sort_and_print(in) reads lines of text from ifstream in (which must
// be open, sorts them, and prints the sorted text to standard output.
void sort_and_print(istream& in) {
  vector<string> v;
  string s;
  while (getline(in, s))
    v.push_back(s);
  sort(v.begin(), v.end());
  for (vector<string>::const_iterator p=v.begin(); p!=v.end(); ++p)
    cout << *p << "\n";
}

// Open argv[1] for reading, or use cin if missing, then sort it.
int main(int argc, char** argv) {
  if (argc>1) {
    ifstream in(argv[1]);
    if (in)
      sort_and_print(in);
    else
      cerr << "File " << argv[1] << " not found\n";
  }
  else
    sort_and_print(cin);
  return 0;
}