Solutions for PWC 80

1 files changed, 66 insertions, 0 deletions

diff --git a/challenge-080/bob-lied/perl/lib/SmallestPositive.pm b/challenge-080/bob-lied/perl/lib/SmallestPositive.pm
new file mode 100644
index 0000000000..f2a4d9635c
--- /dev/null
+++ b/challenge-080/bob-lied/perl/lib/SmallestPositive.pm
@@ -0,0 +1,66 @@
+# vim:set ts=4 sw=4 sts=4 et ai wm=0 nu:
+#=============================================================================
+# SmallestPositive.pm
+#=============================================================================
+# Copyright (c) 2020, Bob Lied
+#=============================================================================
+# Description:
+#=============================================================================
+
+package SmallestPositive;
+
+use strict;
+use warnings;
+use v5.30;
+
+use feature qw/ signatures /;
+no warnings qw/ experimental::signatures /;
+
+use List::MoreUtils qw/ firstidx /;
+
+require Exporter;
+our @ISA = qw(Exporter);
+our @EXPORT = qw();
+our @EXPORT_OK = qw();
+
+sub new($class, @N)
+{
+    $class = ref($class) || $class;
+    my $self = {
+    };
+    bless $self, $class;
+
+    # Clean up the list to have only positive numbers in sorted order
+    $self->{_N} = [ sort { $a <=> $b } grep $_ > 0, @N ];
+    return $self;
+}
+
+sub run($self)
+{
+    my @n = @{$self->{_N}};
+
+    # Weed out some special cases.
+    if ( @n == 0 ) # Empty list
+    {
+        return 1;
+    }
+    elsif ( @n == 1 )
+    {
+        return ($n[0] == 1 ? 2 : 1);
+    }
+
+    # Put a lower bound and upper bound on the list.
+    unshift @n, 0;
+    push @n, ($n[-1] + 2);
+
+    # Calculate differences between pairs.
+    my @delta = map { $n[$_+1] - $n[$_] } ( 0 .. $#n-1 );
+    
+    # Find the first difference that isn't 1.  We rigged the list
+    # to have a +2 at the right end, so there must be one.
+    my $place = firstidx { $_ > 1 } @delta;
+
+    return $n[$place] + 1;
+}
+
+1;