Add yet another solution

3 files changed, 34 insertions, 3 deletions

diff --git a/challenge-113/wlmb/perl/ch-1.pl b/challenge-113/wlmb/perl/ch-1.pl
index dd45af20c1..d0557028eb 100755
--- a/challenge-113/wlmb/perl/ch-1.pl
+++ b/challenge-113/wlmb/perl/ch-1.pl
@@ -1,6 +1,6 @@
 #!/usr/bin/env perl
 # Perl weekly challenge 113
-# Task 1: Represent integer.
+# Task 1: Represent integer. Faster, recursive
 #
 # See https://wlmb.github.io/2021/05/22/PWC113/#task-1-represent-integer
 use strict;
@@ -21,7 +21,6 @@ say("Inputs: N=$N D=$D: Output: ",
 
 sub find {
     my ($goal, @set)=@_;
-    die "Shouldn't happen" if $goal==0;
     while(defined (my $current=shift @set)){
 	next if $current > $goal;
 	return ($current) if $current==$goal;
diff --git a/challenge-113/wlmb/perl/ch-1a.pl b/challenge-113/wlmb/perl/ch-1a.pl
index 7ae51a652c..aafb16bbdc 100755
--- a/challenge-113/wlmb/perl/ch-1a.pl
+++ b/challenge-113/wlmb/perl/ch-1a.pl
@@ -1,6 +1,6 @@
 #!/usr/bin/env perl
 # Perl weekly challenge 113
-# Task 1: Represent integer.
+# Task 1: Represent integer. Slow, exhaustive
 #
 # See https://wlmb.github.io/2021/05/22/PWC113/#task-1-represent-integer
 use strict;
diff --git a/challenge-113/wlmb/perl/ch-1b.pl b/challenge-113/wlmb/perl/ch-1b.pl
new file mode 100755
index 0000000000..eb9ca9a0b1
--- /dev/null
+++ b/challenge-113/wlmb/perl/ch-1b.pl
@@ -0,0 +1,32 @@
+#!/usr/bin/env perl
+# Perl weekly challenge 113
+# Task 1: Represent integer. Even faster, recursive with cutoff.
+#
+# See https://wlmb.github.io/2021/05/22/PWC113/#task-1-represent-integer
+use strict;
+use warnings;
+use v5.12;
+use List::Util qw(sum0);
+use POSIX qw(floor);
+
+my ($N, $D)=@ARGV; #get arguments from command line.
+die "Usage: ./ch-1b.pl positive-integer digit"
+    unless defined $N and defined $D and $N>=0
+    and $D=~m/^\d$/ and $N==floor $N;
+say("Inputs: N=$N D=$D: Output: 1 as $N>=",$D*10), exit if $N>=$D*10;
+my @set=reverse grep {m/$D/} (1..$N); # ordered set from large to small.
+my @answer=find($N,@set);
+say("Inputs: N=$N D=$D: Output: ",
+    @answer? "1 as $N=". join("+", @answer):"0");
+
+
+sub find {
+    my ($goal, @set)=@_;
+    while(defined (my $current=shift @set)){
+	next if $current > $goal;
+	return ($current) if $current==$goal;
+	my @answer=find($goal-$current, @set);
+	return ($current,@answer) if @answer;
+    }
+    return ();
+}