Task 2: this time with a SINGLY-linked list

1 files changed, 120 insertions, 0 deletions

diff --git a/challenge-071/dave-jacoby/perl/ch-2b.pl b/challenge-071/dave-jacoby/perl/ch-2b.pl
new file mode 100755
index 0000000000..e390ff3eff
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+++ b/challenge-071/dave-jacoby/perl/ch-2b.pl
@@ -0,0 +1,120 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say signatures state };
+no warnings qw{ experimental };
+
+use Getopt::Long;
+my $n = 1;
+GetOptions( 'number=i' => \$n, );
+
+my $start = Node->new('0');
+for my $i ( 1 .. 5 ) {
+    my $last = get_last($start);
+    $last->next( Node->new($i) );
+}
+
+# show_list($start->next); #so we don't get the start node
+trim_list( $start, $n );
+
+exit;
+
+sub trim_list ( $link, $n = 1 ) {
+
+    # how big is the linked list?
+    my $i = 0;
+    my $s = $link;
+
+    while ( defined $s ) {
+        $i++;
+        $s = $s->{next};
+    }
+    my $stop = $i - $n;
+    $stop = $stop < 1 ? 1 : $stop;
+
+    my $k = 1;
+    $s = $link;
+    while ( $s->next ) {
+        if ( $stop == $k ) {
+            $s->remove_next;
+            last;
+        }
+        $s = $s->next;
+        $k++;
+    }
+    show_list( $start->next );
+}
+
+sub show_list( $link ) {
+    while ( defined $link ) {
+        print $link->{value} || '';
+        if ( defined $link->{next} ) {
+            print ' -> '
+                if defined $link->{next};
+        }
+        else { print "\n" if !defined $link->{next}; }
+        $link = $link->{next};
+    }
+}
+
+sub get_last( $node ) {
+    return get_last( $node->next ) if $node->next;
+    return $node;
+}
+
+# copied and pasted from my Challenge #59 code
+
+######### ######### ######### ######### ######### ######### #########
+# The same old Node code, but instead of left and right,
+# it just has next
+
+######### ######### ######### ######### ######### ######### #########
+# Now a singly-linked list, meaning no pointing back to the start
+
+package Node;
+
+sub new ( $class, $value = 0 ) {
+    my $self = {};
+    $self->{value} = $value;
+    $self->{next}  = undef;
+
+    # $self->{parent} = undef;
+    return bless $self, $class;
+}
+
+sub value ( $self ) {
+    return $self->{value};
+}
+
+# sub is_root ( $self ) {
+#     return defined $self->{parent} ? 0 : 1;
+# }
+
+sub is_leaf ( $self ) {
+    return ( !defined $self->{left} && !defined $self->{right} )
+        ? 1
+        : 0;
+}
+
+sub next ( $self, $node = undef ) {
+    if ( defined $node ) {
+        $self->{next} = $node;
+
+        # $node->{parent} = $self;
+    }
+    else {
+        return $self->{next};
+    }
+}
+
+# sub parent ($self ) {
+#     return $self->{parent};
+# }
+
+sub remove_next( $self ) {
+    my $next = $self->{next};
+    if ( defined $next ) {
+        $self->{next} = $next->{next};
+    }
+}