#020 solutions

4 files changed, 96 insertions, 0 deletions

diff --git a/challenge-020/feng-chang/perl5/ch-1.pl b/challenge-020/feng-chang/perl5/ch-1.pl
new file mode 100755
index 0000000000..b34ce16cdb
--- /dev/null
+++ b/challenge-020/feng-chang/perl5/ch-1.pl
@@ -0,0 +1,35 @@
+#!/bin/env perl
+
+use Modern::Perl;
+
+die "usage: $0 <string>\n" unless $ARGV[0];
+
+say 'Solution 1:';
+{
+    my @a;
+    my $last_char = '';
+    my $s = '';
+    for my $c (split //, $ARGV[0]) {
+        if ($c eq $last_char) {
+            $s .= $c;
+        } else {
+            push(@a, $s) if $s;
+            $s = $last_char = $c;
+        }
+    }
+    push(@a, $s) if $s;
+
+    say join ' ', @a;
+}
+
+say 'Solution 2:';
+{
+    my @a;
+    my $i = 1;
+    for my $s ($ARGV[0] =~ m/((.)\2*)/g) {
+        push(@a, $s) if $i;
+        $i = 1 - $i;
+    }
+
+    say join ' ', @a;
+}
diff --git a/challenge-020/feng-chang/perl5/ch-2.pl b/challenge-020/feng-chang/perl5/ch-2.pl
new file mode 100755
index 0000000000..5d68276e7c
--- /dev/null
+++ b/challenge-020/feng-chang/perl5/ch-2.pl
@@ -0,0 +1,47 @@
+#!/bin/env perl
+
+use Modern::Perl;
+use integer;
+
+my $i = 0;
+my %sods;
+my $cnt = 0;
+
+while (1) {
+    $sods{ $i } = sod($i) unless defined $sods{ $i };
+    my $v = $sods{ $i };
+    
+    if ($v > $i) {
+        $sods{ $v } = sod($v) unless defined $sods{ $v };
+        if ($i == $sods{ $v }) {
+            say "$i $v";
+            last if ++$cnt == 5;
+        }
+    }
+
+    ++$i;
+}
+
+# sum of proper divisors
+sub sod {
+    my $n = shift;
+
+    my $sum = 0;
+    my @a = (1) x ($n/2 + 1);
+
+    for (my $i = 1; $i < $n/2 + 1; ++$i) {
+        next unless $a[$i];
+
+        if ($n % $i) {
+            my $j = $i;
+            while ($j <= $n/2 + 1) {
+                $a[$j] = 0;
+                $j += $i;
+            }
+        } else {
+            $sum += $i;
+        }
+    }
+
+    return $sum;
+}
diff --git a/challenge-020/feng-chang/perl6/ch-1.p6 b/challenge-020/feng-chang/perl6/ch-1.p6
new file mode 100755
index 0000000000..5e737a5950
--- /dev/null
+++ b/challenge-020/feng-chang/perl6/ch-1.p6
@@ -0,0 +1,3 @@
+#!/bin/env perl6
+
+sub MAIN($str = 'ABBCDEEF') { $str.comb(/(.)$0*/).say }
diff --git a/challenge-020/feng-chang/perl6/ch-2.p6 b/challenge-020/feng-chang/perl6/ch-2.p6
new file mode 100755
index 0000000000..a7fd1d71cb
--- /dev/null
+++ b/challenge-020/feng-chang/perl6/ch-2.p6
@@ -0,0 +1,11 @@
+#!/bin/env perl6
+
+my @a = (0..∞).map:  { sod($_) };
+my @b = (0..∞).grep: { @a[$_] > $_ and @a[@a[$_]] == $_ };
+
+say(@b[0], ' ', @a[@b[0]]);
+
+# sum of proper divisors
+sub sod(UInt $n) {
+    [+] (1 .. $n/2).grep: { $n %% $_ }
+}