Data commit

Task/Partition-function-P/Perl/partition-function-p.pl

@@ -0,0 +1,29 @@
+use strict;
+use warnings;
+no warnings qw(recursion);
+use Math::AnyNum qw(:overload);
+use Memoize;
+
+memoize('partitionsP');
+memoize('partDiff');
+
+sub partDiffDiff { my($n) = @_; $n%2 != 0 ? ($n+1)/2 : $n+1 }
+
+sub partDiff { my($n) = @_; $n<2 ? 1 : partDiff($n-1) + partDiffDiff($n-1) }
+
+sub partitionsP {
+    my($n) = @_;
+    return 1 if $n < 2;
+
+    my $psum = 0;
+    for my $i (1..$n) {
+        my $pd = partDiff($i);
+        last if $pd > $n;
+        if ( (($i-1)%4) < 2 ) { $psum += partitionsP($n-$pd) }
+        else                  { $psum -= partitionsP($n-$pd) }
+    }
+    return $psum
+}
+
+print partitionsP($_) . ' ' for 0..25; print "\n";
+print partitionsP(6666) . "\n";