#!/usr/bin/perl -w

use strict;

sub diff4 {
	my $strings = shift;

	my %start_set_by_l_token;
	my %l_by_start;
	my %l_by_end;

	{
		my %start_set_by_token;
		my $I = 0;
		for my $s (@$strings) {
			my $sl = length $s;
			for (my $i=0; $i<$sl; ++$i) {
				my $start = "${I}_$i";
				my $substr = substr $s, $i, 1;
				$start_set_by_token{$substr}{$start} = 1;
			}
			$I++;
		}
		
		while (my ($substr, $start_set) = each %start_set_by_token) {
			if (keys %$start_set == 1) {
				delete $start_set_by_token{$substr}
			} else {
				for my $start (keys %$start_set) {
					my ($I, $i) = split /_/, $start, 2;
					$l_by_start{$start} = 1;
					$l_by_end{$I."_".($i+$l)} = 1;
				}
			}
		}
		
		$start_set_by_l_token{1} = \%start_set_by_token;
	}

	my @start_sorted = map {$_->[0]}
		sort { $a->[1] <=> $b->[1] || $a->[2] <=> $b->[2] }
			map {[$_, split /_/, $_]}
				keys %l_by_start;

	for my $start (@start_sorted) {
		my ($I, $i) = split /_/, $start, 2;
		my $can_join_start
		if ($l_by_end{$start}) {
			
		}
	}
	
	my $l;
	for ($l=2; ; ++$l) {
		my %start_set_by_token;
		my $I = 0;
		while (my ($substr, $start_set) = each %{$start_set_by_l_token{$l-1}}) {
			for my $start (keys %$start_set) {
				my ($I, $i) = split /_/, $start, 2;
				my $s = $$strings[$I];
				my $sl = length $s;
				if ($i <= $sl-$l) {
					my $substr = substr $s, $i, $l;
					$start_set_by_token{$substr}{$start} = 1;
				}
			}
		}
		
		while (my ($substr, $start_set) = each %start_set_by_token) {
			delete $start_set_by_token{$substr} if keys %$start_set == 1;
		}

		last if keys %start_set_by_token == 0;
		
		$start_set_by_l_token{$l} = \%start_set_by_token;
	}

	my $n = $l;
}