Cycle detection: Difference between revisions
Added Perl example
SqrtNegInf (talk | contribs) (Added Perl example) |
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Cycle = 101 2 5 26 167 95
</pre>
=={{header|Perl}}==
{{trans|Perl 6}}
<lang perl>use utf8;
sub cyclical_function { ($_[0] * $_[0] + 1) % 255 }
sub brent {
my($f, $x0) = @_;
my $power = 1;
my $λ = 1;
my $tortoise = $x0;
my $hare = &$f($x0);
while ($tortoise != $hare) {
if ($power == $λ) {
$tortoise = $hare;
$power *= 2;
$λ = 0;
}
$hare = &$f($hare);
$λ += 1;
}
my $μ = 0;
$tortoise = $hare = $x0;
$hare = &$f($hare) for 0..$λ-1;
while ($tortoise != $hare) {
$tortoise = &$f($tortoise);
$hare = &$f($hare);
$μ += 1;
}
return $λ, $μ;
}
my ( $l, $s ) = brent( \&cyclical_function, 3 );
sub show_range {
my($start,$stop) = @_;
my $result;
my $x = 3;
for my $n (0..$stop) {
$result .= "$x " if $n >= $start;
$x = cyclical_function($x);
}
$result;
}
print show_range(0,19) . "\n";
print "Cycle length $l\n";
print "Cycle start index $s\n";
print show_range($s,$s+$l-1) . "\n";</lang>
{{out}}
<pre>3 10 101 2 5 26 167 95 101 2 5 26 167 95 101 2 5 26 167 95
Cycle length 6
Cycle start index 2
101 2 5 26 167 95</pre>
=={{header|Perl 6}}==
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