1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/src/collatz.pl	Tue Oct 18 01:17:49 2011 -0700
     1.3 @@ -0,0 +1,69 @@
     1.4 +#!/usr/bin/perl
     1.5 +
     1.6 +use bigint;
     1.7 +$a = "/home/r/coderloop-test/euler14-a.in";
     1.8 +$b = "/home/r/coderloop-test/euler14-b.in";
     1.9 +
    1.10 +sub read_integer{
    1.11 +  ##reads an integer from a file
    1.12 +  (my $file) = @_;
    1.13 +  my $int;
    1.14 +  open FILE, "<".$file or die $!;
    1.15 +  for (<FILE>){ chomp; /^\W*(\d+)\W*$/; $int = $1;}
    1.16 +  close FILE;
    1.17 +  return $int;}
    1.18 +
    1.19 +
    1.20 +@collatz = (1);
    1.21 +
    1.22 +
    1.23 +sub collatz_next {
    1.24 +  my $n = @_[0];
    1.25 +  if (1 == $n) {return 1;}
    1.26 +  if (0 == ($n % 2)){ return $n/2;}
    1.27 +  if (1 == ($n % 2)){ return (($n*3)+1);}
    1.28 +}
    1.29 +
    1.30 +sub different_collatz_length {
    1.31 +  my $n = $_[0];
    1.32 +  my $d = 1;
    1.33 +  while ($n != 1){
    1.34 +    $d++;
    1.35 +    $n = collatz_next($n);}
    1.36 +  return $d;}
    1.37 +
    1.38 +sub collatz_length {
    1.39 +  ## calculate the length of the collatz sequence 
    1.40 +  ## http://en.wikipedia.org/wiki/Collatz_conjecture
    1.41 +  ## starting at n
    1.42 +  my $n = @_[0];
    1.43 +  #print $n,"\n";
    1.44 +  #memoization
    1.45 +  #print "***** ", $collatz[$n], " ********\n";
    1.46 +  if (defined $collatz[$n]){return $collatz[$n];}
    1.47 +  if (1 == $n) {return 1;}
    1.48 +  if (0 == ($n % 2)){ return (1 + &collatz_length($n/2))}
    1.49 +  if (1 == ($n % 2)){ return (1 + &collatz_length(($n*3)+1));}
    1.50 +}
    1.51 +
    1.52 +
    1.53 +sub max_collatz {
    1.54 +    my $n = @_[0];
    1.55 +    my $max_length = 1;
    1.56 +    my $max_val = 1;
    1.57 +    for (my $i = 1; $i < $n; $i++){
    1.58 +	my $collatz = &different_collatz_length($i);
    1.59 +	#push(@collatz, $collatz);
    1.60 +	if ( $collatz >= $max_length){
    1.61 +	    $max_length = $collatz ;
    1.62 +	    $max_val = $i}}
    1.63 +    print "\n number is : $max_length --- ";
    1.64 +    print &collatz_length($max_val) . "\n";
    1.65 +    return $max_val;
    1.66 +}
    1.67 +
    1.68 +
    1.69 +
    1.70 +
    1.71 +if (defined @ARGV){
    1.72 +    print &max_collatz(read_integer($ARGV[0])), "\n";}