1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/src/reverse_seq.pl	Tue Oct 18 01:17:49 2011 -0700
     1.3 @@ -0,0 +1,43 @@
     1.4 +#!/usr/bin/perl
     1.5 +
     1.6 +$a = "/home/r/coderloop-test/reversesequence-a.in";
     1.7 +$b = "/home/r/coderloop-test/reversesequence-b.in";
     1.8 +$c = "/home/r/coderloop-test/reversesequence-c.in";
     1.9 +
    1.10 +%test_map = ("a" => "b", "b" => "c");
    1.11 +
    1.12 +sub create_map{
    1.13 +  ## creates a "linked map" from a string representing
    1.14 +  ## the input file.
    1.15 +  (my $file) = @_;
    1.16 +  my %map;
    1.17 +  open FILE, "<".$file or die $!;
    1.18 +  for (<FILE>){ chomp; /^(\w+)\W+(\w+)$/; $map{$1} = $2;}
    1.19 +  close FILE;
    1.20 +  return %map;}
    1.21 +
    1.22 +sub find_beginning{
    1.23 +  ## takes a map representing a linked list and
    1.24 +  ## returns the beginning of that list.
    1.25 +  (my %map) = @_;
    1.26 +  my %val_set = map {$_ => 1} (values %map);
    1.27 +  my $start;
    1.28 +  foreach (keys %map){
    1.29 +    if (!($val_set{$_})){$start = $_;last}}
    1.30 +  return $start;}
    1.31 +
    1.32 +sub trace_map{
    1.33 +  ## crawls through a map representing a linked-list
    1.34 +  ## and converts it into an actual array structure.
    1.35 +  (my %map) = @_;
    1.36 +  my $position = &find_beginning(%map);
    1.37 +  my @array = ($position);
    1.38 +  while(my $new_position = $map{$position}){
    1.39 +    push (@array, $new_position);
    1.40 +    $position = $new_position;}
    1.41 +  return @array;}
    1.42 +
    1.43 +
    1.44 +
    1.45 +if (defined @ARGV){
    1.46 +  map {print;print"\n";} reverse(trace_map(create_map($ARGV[0])));}