Merge pull request #4851 from wlmb/challenges

Solve PWC 129

3 files changed, 70 insertions, 0 deletions

diff --git a/challenge-129/wlmb/blog.txt b/challenge-129/wlmb/blog.txt
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index 0000000000..083e05156d
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+++ b/challenge-129/wlmb/blog.txt
@@ -0,0 +1 @@
+https://wlmb.github.io/2021/09/06/PWC129/
diff --git a/challenge-129/wlmb/perl/ch-1.pl b/challenge-129/wlmb/perl/ch-1.pl
new file mode 100755
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+++ b/challenge-129/wlmb/perl/ch-1.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 129
+# Task 1:  root distance
+#
+# See https://wlmb.github.io/2021/09/06/PWC129/#task-1-root-distance
+use warnings;
+use strict;
+use v5.12;
+# use Data::Dumper;
+
+my %root_distance; # hash of depths indexed by the node values.
+# my $tree=   # Throw away the actual tree, as it is not used
+analyze_tree(-1,-1); # initialize indentation and depth.
+# say Dumper($tree); # For debugging
+say "Value: $_ Depth: ", $root_distance{$_}//"Not defined" for @ARGV;
+
+sub analyze_tree {
+    my ($previous_indent, $depth)=@_;
+    ++$depth;
+    my ($current_indent, $value)=analyze_line($previous_indent);
+    # If I found a node at the correct indentation, build a tree structure
+    $root_distance{$value}=$depth, #
+        return {value=>$value,
+            left=>analyze_tree($current_indent,$depth),
+            right=>analyze_tree($current_indent,$depth)}
+        if defined $current_indent && defined $value && $value ne '';
+    return undef;
+}
+
+sub analyze_line {
+# Read and analyze lines. Keep them until their turn if outdented
+    state ($line, $current_indent, $value);
+    my $previous_indent=shift;
+    if(!defined $current_indent){
+	$line=<STDIN>;
+	return () if !defined $line || $line=~m/^\s*$/;
+	die "Malformed tree: $line" unless $line=~m/^(\s*)-\s*(\d*)\s*$/;
+	$current_indent=length $1;
+	$value=$2;
+    }
+    if($current_indent>$previous_indent){
+	my $result_indent=$current_indent;
+	$current_indent=undef;
+	return ($result_indent, $value);
+    }
+    return ();
+}
diff --git a/challenge-129/wlmb/perl/ch-2.pl b/challenge-129/wlmb/perl/ch-2.pl
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+++ b/challenge-129/wlmb/perl/ch-2.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 129
+# Task 2:  add linked lists
+#
+# See https://wlmb.github.io/2021/09/06/PWC129/#task-2-add-linked-lists
+use warnings;
+use strict;
+use v5.12;
+use List::Util qw(all);
+use bigint; # to allow large lists
+my @A=split /\s*->\s*/, shift @ARGV;
+my @B=split /\s*->\s*/, shift @ARGV;
+die "Usage: ./ch-2.pl l1 l2 with list arguments of the form \"dN...d2->d1->d0\""
+    unless all {m/^\d$/} @A, @B;
+my $A=join '', @A;
+my $B=join '', @B;
+my $length=@A-@B;
+my $indent_A=$length<0?"   "x(-$length):"";
+my $indent_B=$length>0?"   "x  $length :"";
+say "Input: L1=$indent_A", join "->", @A;
+say "       L2=$indent_B", join "->", @B;
+say "Output:   ", join "->", split '', $A+$B;