# This function removes the duplicates in @candidates & returns a hash of candidates (%candidates)
# which contains candidates & their number of occurences in @candidates
# This function take as argument the list of candidates (@candidates)
sub clean_candidates {
    my ($this,@candidates) =  @_;
    my %candidates = (); # my %candidates ( $candidate => $nbOcc );
    foreach my $candidate (@candidates){
        $candidates{$candidate} ++;
    }
my %sorted_candidates = sort ({ $candidates{$a} <=> $candidates{$b} } %candidates);
    return %sorted_candidates;
}