Mercurial > coderloop

     1 #!/usr/bin/perl

     2 

     3 $a = "/home/r/coderloop-test/reversesequence-a.in";

     4 $b = "/home/r/coderloop-test/reversesequence-b.in";

     5 $c = "/home/r/coderloop-test/reversesequence-c.in";

     6 

     7 %test_map = ("a" => "b", "b" => "c");

     8 

     9 sub create_map{

    10   ## creates a "linked map" from a string representing

    11   ## the input file.

    12   (my $file) = @_;

    13   my %map;

    14   open FILE, "<".$file or die $!;

    15   for (<FILE>){ chomp; /^(\w+)\W+(\w+)$/; $map{$1} = $2;}

    16   close FILE;

    17   return %map;}

    18 

    19 sub find_beginning{

    20   ## takes a map representing a linked list and

    21   ## returns the beginning of that list.

    22   (my %map) = @_;

    23   my %val_set = map {$_ => 1} (values %map);

    24   my $start;

    25   foreach (keys %map){

    26     if (!($val_set{$_})){$start = $_;last}}

    27   return $start;}

    28 

    29 sub trace_map{

    30   ## crawls through a map representing a linked-list

    31   ## and converts it into an actual array structure.

    32   (my %map) = @_;

    33   my $position = &find_beginning(%map);

    34   my @array = ($position);

    35   while(my $new_position = $map{$position}){

    36     push (@array, $new_position);

    37     $position = $new_position;}

    38   return @array;}

    39 

    40 

    41 

    42 if (defined @ARGV){

    43   map {print;print"\n";} reverse(trace_map(create_map($ARGV[0])));}
author	Robert McIntyre <rlm@mit.edu>
date	Tue, 18 Oct 2011 01:17:49 -0700
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