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copied!<h2>Perl</h2> <p>With input validation/pre-sorting</p> <p>You can easily get the result as a LoL if you need to do something more fancy than just return a string.</p> <pre><code>#!/usr/bin/perl -w use strict; use warnings; use Scalar::Util qw/looks_like_number/; sub adjacenify { my @input = @_; # Validate and sort looks_like_number $_ or die "Saw '$_' which doesn't look like a number" for @input; @input = sort { $a <=> $b } @input; my (@output, @range); @range = (shift @input); for (@input) { if ($_ - $range[-1] <= 1) { push @range, $_ unless $range[-1] == $_; # Prevent repetition } else { push @output, [ @range ]; @range = ($_); } } push @output, [ @range ] if @range; # Return the result as a string. If a sequence is size 1, then it's just that number. # Otherwise, it's the first and last number joined by '-' return join ', ', map { 1 == @$_ ? @$_ : join ' - ', $_->[0], $_->[-1] } @output; } print adjacenify( qw/1 2 3 5 7 9 10 11 12 14/ ), "\n"; print adjacenify( 1 .. 5 ), "\n"; print adjacenify( qw/-10 -9 -8 -1 0 1 2 3 5 7 9 10 11 12 14/ ), "\n"; print adjacenify( qw/1 2 4 5 6 7 100 101/), "\n"; print adjacenify( qw/1 62/), "\n"; print adjacenify( qw/1/), "\n"; print adjacenify( qw/1 2/), "\n"; print adjacenify( qw/1 62 63/), "\n"; print adjacenify( qw/-2 0 0 2/), "\n"; print adjacenify( qw/-2 0 0 1/), "\n"; print adjacenify( qw/-2 0 0 1 2/), "\n"; </code></pre> <p>Output:</p> <pre><code>1 - 3, 5, 7, 9 - 12, 14 1 - 5 -10 - -8, -1 - 3, 5, 7, 9 - 12, 14 1 - 2, 4 - 7, 100 - 101 1, 62 1 1 - 2 1, 62 - 63 -2, 0, 2 -2, 0 - 1 -2, 0 - 2 -2, 0 - 2 </code></pre> <p>And a nice recursive solution:</p> <pre><code>sub _recursive_adjacenify($$); sub _recursive_adjacenify($$) { my ($input, $range) = @_; return $range if ! @$input; my $number = shift @$input; if ($number - $range->[-1] <= 1) { return _recursive_adjacenify $input, [ @$range, $number ]; } else { return $range, _recursive_adjacenify $input, [ $number ]; } } sub recursive_adjacenify { my @input = @_; # Validate and sort looks_like_number $_ or die "Saw '$_' which doesn't look like a number" for @input; @input = sort { $a <=> $b } @input; my @output = _recursive_adjacenify \@input, [ shift @input ]; # Return the result as a string. If a sequence is size 1, # then it's just that number. # Otherwise, it's the first and last number joined by '-' return join ', ', map { 2 == @$_ && $_->[0] == $_->[1] ? $_->[0] : 1 == @$_ ? @$_ : join ' - ', $_->[0], $_->[-1] } @output; } </code></pre>

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