éliminer les doublons !

#include <conio.h> //au lieu de #include <conio.c>

fprintf(File, "%s\n%s\n", mail , mail );// enregistre dans le fichier en désordre

//l'option -u permet de gérer l'unicité
system("sort -u mail.txt>>ordre.txt");//classe par ordre alpha

#include <iostream>
#include <iomanip>
#include <set>
#include <cstdlib>
#include <fstream>

/*!
** Get a random number between min and max
**
** @param min The lower limit
** @param max The upper limit
**
** @return A random number
*/
int randi(int min, int max)
{
  return (min + (rand() % (max - min + 1)));
}

/*!
** Generate mail with a given size
**
** @param longueur The size of the mail
**
** @return A random mail
*/
std::string generateMail(int longueur)
{
  char mail[32] = {0};

  for (int j = 0; j < longueur; ++j)
    switch (randi(1, 2))
    {
      case 1:
	mail[j] = randi('-', '.');
	break;
      case 2:
	mail[j] = randi('a', 'z');
	break;
    }

  return mail;
}

/*!
** Fill a set with random mails
**
** @param mail The mail list
** @param nb Number of mail to add
** @param longueur Size of each mail
*/
void genMails(std::set<std::string>& mail, int nb, int longueur)
{
  for (int i = 1; i <= nb; ++i)
    mail.insert(generateMail(longueur));
}

/*!
** Display mails
**
** @param mail The mail list
*/
void displayMail(const std::set<std::string>& mail)
{
  typedef std::set<std::string>::const_iterator iter;
  for (iter it = mail.begin(); it != mail.end(); ++it)
    std::cout << *it << std::endl;
}

/*!
** Copy each mail into a file
**
** @param filename The file where to copy mail
** @param mail The mail list
*/
void copyMailIntoFile(const std::string& filename,
		      const std::set<std::string>& mail)
{
  typedef std::set<std::string>::const_iterator iter;
  std::ofstream file(filename.c_str(), std::ios::out | std::ios::trunc);

  if (!file)
  {
    std::cerr << "Impossible d'écrire dans le fichier" << std::endl;
    return;
  }

  for (iter it = mail.begin(); it != mail.end(); ++it)
    file<< *it << std::endl;

  file.close();
}

/*!
** The entry point :)
**
** @return 0
*/
int main()
{
  int number = 0;
  std::set<std::string> mail;
  const std::string filename = "mail.txt";

  srand(time(NULL));
  std::cout << "Nombre de mail à générer" << std::endl;
  std::cin >> number;
  genMails(mail, number, 7);

//   displayMail(mail);
  copyMailIntoFile(filename, mail);

  return 0;
}