Printing all the permutations of a string in alphabetical order

Question

It is a code eval challenge question https://www.codeeval.com/open_challenges/14/. My answer was accepted, and I modified my code again to improve it. Please let me know is it possible to improve it more.

#include <iostream>
#include<fstream>
#include<algorithm>
#include<string>
void create_permute( std::string &record )
{
 if( !record.empty() ) 
 {
 std::sort( record.begin(), record.end() );
 bool flag=0;
 do{
 if( flag )
 {
 std::cout<<",";
 }
 flag = 1;
 std::cout << record;
 } while( std::next_permutation( record.begin(), record.end() ) );
 std::cout << "\n";
 }
}
void readInputFile( std::string filename ) 
{
 std::ifstream infile;
 infile.open( filename );
 std::string record;
 while( std::getline( infile,record ) )
 { 
 create_permute( record );
 }
}
int main( int argc, char* argv[] )
{
 if( argc < 2 )
 {
 std::cout << "usage: filesize filename" << "\n";
 exit( 0 );
 }
 std::ios_base::sync_with_stdio( false );
 readInputFile( argv[ 1 ] );
 return 0;
}

Answer 1

If you have preconditions return early

if( !record.empty() ) 
{
 // CODE
}
// If the precondition for doing work is that it is not empty
// Then test and return immediately.
if (record.empty()) {
 return;
}
// CODE

Now your code does not suffer lots of indenting and becomes easier to read.

Use constructors

std::ifstream infile;
infile.open( filename );
// Easier to read and write as:
std::ifstream infile( filename );

I think we can simplify that loop:

std::sort( record.begin(), record.end() );
std::cout << record;
while( std::next_permutation( record.begin(), record.end() ))
{
 std::cout << ", " << record
}
std::cout << "\n";

Answer 2

A boolean tested each time, and firing just once on the first iteration is unaesthetic (and a waste of time). Consider instead

 std::cout << record;
 while (std::next_permutation(record.begin(), record.end())) {
 std::cout << ',' << record;
 }
 std::cout << '\n';

Otherwise looks good. Congratulations for not using namespace std.

Answer 3

It's a good habit to eliminate special cases from your code. I don't see any particular reason to check for if ( !record.empty() ), so don't.

Answer 4

As long as you know for a fact that std::ifstream automatically at the end of void readInputFile( std::string ), there is nothing to add besides what already @vpn and @200_success said.