Mercurial > coderloop

     1 #!/usr/bin/perl

     2 

     3 use bigint;

     4 $a = "/home/r/coderloop-test/euler14-a.in";

     5 $b = "/home/r/coderloop-test/euler14-b.in";

     6 

     7 sub read_integer{

     8   ##reads an integer from a file

     9   (my $file) = @_;

    10   my $int;

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

    12   for (<FILE>){ chomp; /^\W*(\d+)\W*$/; $int = $1;}

    13   close FILE;

    14   return $int;}

    15 

    16 

    17 @collatz = (1);

    18 

    19 

    20 sub collatz_next {

    21   my $n = @_[0];

    22   if (1 == $n) {return 1;}

    23   if (0 == ($n % 2)){ return $n/2;}

    24   if (1 == ($n % 2)){ return (($n*3)+1);}

    25 }

    26 

    27 sub different_collatz_length {

    28   my $n = $_[0];

    29   my $d = 1;

    30   while ($n != 1){

    31     $d++;

    32     $n = collatz_next($n);}

    33   return $d;}

    34 

    35 sub collatz_length {

    36   ## calculate the length of the collatz sequence 

    37   ## http://en.wikipedia.org/wiki/Collatz_conjecture

    38   ## starting at n

    39   my $n = @_[0];

    40   #print $n,"\n";

    41   #memoization

    42   #print "***** ", $collatz[$n], " ********\n";

    43   if (defined $collatz[$n]){return $collatz[$n];}

    44   if (1 == $n) {return 1;}

    45   if (0 == ($n % 2)){ return (1 + &collatz_length($n/2))}

    46   if (1 == ($n % 2)){ return (1 + &collatz_length(($n*3)+1));}

    47 }

    48 

    49 

    50 sub max_collatz {

    51     my $n = @_[0];

    52     my $max_length = 1;

    53     my $max_val = 1;

    54     for (my $i = 1; $i < $n; $i++){

    55 	my $collatz = &different_collatz_length($i);

    56 	#push(@collatz, $collatz);

    57 	if ( $collatz >= $max_length){

    58 	    $max_length = $collatz ;

    59 	    $max_val = $i}}

    60     print "\n number is : $max_length --- ";

    61     print &collatz_length($max_val) . "\n";

    62     return $max_val;

    63 }

    64 

    65 

    66 

    67 

    68 if (defined @ARGV){

    69     print &max_collatz(read_integer($ARGV[0])), "\n";}
author	Robert McIntyre <rlm@mit.edu>
date	Tue, 18 Oct 2011 01:17:49 -0700
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