#! /usr/bin/perl
use warnings;
use strict;

use enum qw[ LINE POS LENGTH ];


my %string_at;

sub overlap {
    my @s = @_;
    my (@from, @to);
    for my $string (@s) {
        my ($pos, $length) = @{ $string_at{$string} }[ POS, LENGTH ];
        push @from, $pos;
        push @to, $pos + $length - 1;
    }
    if ($from[1] < $from[0]) {
        @from = reverse @from;
        @to   = reverse @to;
    }
    return $to[0] >= $from[1]
}

sub output {
    my @strings = sort { $string_at{$a}[LINE] <=> $string_at{$b}[LINE]
                           ||
                         $string_at{$a}[POS]  <=> $string_at{$b}[POS]
                  } keys %string_at;
    my ($prev_line, $prev_pos) = (0, 0);

    for my $string (@strings) {
        my ($line, $pos, $length) = @{ $string_at{$string} };
        if ($line != $prev_line) {
            print "\n";
            $prev_line = $line;
            $prev_pos  = 0;
        }
        print ' ' x ($pos - $prev_pos + 1), $string;
        $prev_pos = $pos + $length + 1;
    }
    print "\n";
}


my %line_contains;
while (my $line = <DATA>) {
    chomp $line;
    my ($left_spaces) = $line =~ /^#( *)/;
    my $pos = 1 + length $left_spaces;

    my ($right_spaces) = $line =~ /( *)$/;
    my $length = length($line) - $pos - length $right_spaces;

    my $string = substr $line, $pos, $length;
    $string_at{$string} = [ $. - 1, $pos, $length ];
    undef $line_contains{ $. - 1 }{$string};
}


my $change = 1;
while ($change) {
    undef $change;
    for my $string (keys %string_at) {
      TARGET:
        for my $target (0 .. keys(%line_contains) - 1) {
            last TARGET if exists $line_contains{$target}{$string};

            for my $already (keys %{ $line_contains{$target} }) {
                next TARGET if overlap($string, $already);
            }

            my $old_line = $string_at{$string}[LINE];
            $string_at{$string}[LINE] = $target;
            delete $line_contains{$old_line}{$string};
            undef  $line_contains{$target}{$string};
            $change = 1;
            last TARGET
        }
    }
}


output();

__DATA__
#                | compressed
#                   | deleted
#                    | this
#                         | that
#                               | other
#                                 | something else
#                                           | and another
#                                                     foo |
#                                                       bar |
#                                                                     
+   up |
#                                                                     
+  down |
#                                                                    s
+ideways |
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