Merge pull request #313 from jmaslak/joelle-14-2-1

Solution to 14.1 in P6 and P5

2 files changed, 94 insertions, 0 deletions

diff --git a/challenge-014/joelle-maslak/perl5/ch-1.pl b/challenge-014/joelle-maslak/perl5/ch-1.pl
new file mode 100755
index 0000000000..583a8d3956
--- /dev/null
+++ b/challenge-014/joelle-maslak/perl5/ch-1.pl
@@ -0,0 +1,50 @@
+#!/usr/bin/env perl
+use v5.22;
+use strict;
+use warnings;
+
+# Turn on method signatures
+use feature 'signatures';
+no warnings 'experimental::signatures';
+
+use autodie;
+
+die("Usage: $0 <number of sequence elements>") unless @ARGV <= 1;
+my $length = $ARGV[0] // 19;
+
+sub MAIN() {
+    say join ' ', map { van_eck($_) } 0..($length-1);
+}
+
+my %cache_by_val = (0 => [0, 1]);
+my @cache_by_pos = (0, 0);
+
+sub van_eck($pos) {
+    return 0 if $pos <= 1;
+
+    return $cache_by_pos[$pos] if exists $cache_by_pos[$pos];
+
+    # Ensure cache is populated
+    for (my $p=0; $p<$pos; $p++) { van_eck($p) }
+
+    my $n = $pos - 1;
+
+    # We know that we must have been called in order.
+    my $prev = van_eck($n);
+
+    my $current;
+    if (exists $cache_by_val{$prev} and scalar($cache_by_val{$prev}->@*) >= 2) {
+        my $m = $cache_by_val{$prev}->[-2];
+        $current = $n - $m;
+    } else {
+        $current = 0;
+    }
+    $cache_by_pos[$pos] = $current;
+    $cache_by_val{$current} = [] unless exists $cache_by_val{$current};
+    push $cache_by_val{$current}->@*, $pos;
+
+    return $current;
+}
+
+MAIN();
+
diff --git a/challenge-014/joelle-maslak/perl6/ch-1.p6 b/challenge-014/joelle-maslak/perl6/ch-1.p6
new file mode 100755
index 0000000000..05f3653422
--- /dev/null
+++ b/challenge-014/joelle-maslak/perl6/ch-1.p6
@@ -0,0 +1,44 @@
+#!/usr/bin/env perl6
+use v6;
+
+#
+# Copyright © 2019 Joelle Maslak
+# All Rights Reserved - See License
+#
+
+sub MAIN(UInt:D $length = 19) {
+    my $seq = lazy gather { for 0..∞ -> $n { take van-eck($n) } }
+
+    say $seq[^$length].join(" ");
+}
+    
+my %cache-by-val = 0 => [0, 1];
+my @cache-by-pos = 0, 0;
+
+multi sub van-eck(0 --> UInt:D) { 0 }
+multi sub van-eck(1 --> UInt:D) { 0 }
+multi sub van-eck(UInt:D $pos --> UInt:D) {
+
+    return @cache-by-pos[$pos] if @cache-by-pos[$pos]:exists;
+
+    # Ensure cache is populated.
+    for ^$pos -> $p { van-eck($p) }
+
+    my $n = $pos - 1;
+
+    # We know that we must have been called in order.
+    my $prev = van-eck($n);
+
+    my $current;
+    if %cache-by-val{$prev} and %cache-by-val{$prev}.elems ≥ 2 {
+        my $m = %cache-by-val{$prev}[*-2];
+        $current = $n - $m;
+    } else {
+        $current = 0;
+    }
+    @cache-by-pos[$pos] = $current;
+    ( %cache-by-val{$current} //= Array.new ).push: $pos;
+
+    return $current;
+}
+