Merge pull request #3217 from drbaggy/master

solns for 95

3 files changed, 128 insertions, 0 deletions

diff --git a/challenge-095/james-smith/perl/Stack.pm b/challenge-095/james-smith/perl/Stack.pm
new file mode 100644
index 0000000000..ff908f0ae2
--- /dev/null
+++ b/challenge-095/james-smith/perl/Stack.pm
@@ -0,0 +1,50 @@
+package Stack;
+
+## The stack is just stored as a blessed array.
+#
+# Methods:
+#  ->push( $value ) -- push value on top of stack (return stack itself)
+#  ->pop( $value )  -- take value off top of stack & return it
+#                      (if stack has no entries return undef/empty value)
+#  ->top( $value )  -- returns the value at the top of the stack
+#                      (if stack has no entries return undef/empty value)
+#  ->min( $value )  -- returns the smallest value in the stack
+#                      (if stack has no entries return undef/empty value)
+
+
+sub new {
+  my $class = shift;
+  my $self = [];
+  bless $self, $class;
+  return $self;
+}
+
+sub push {
+  my( $self,$val ) = @_;
+  CORE::push @{$self}, $val; ## Make clear we are using the core push method
+  return $self;
+}
+
+sub pop {
+  my $self = shift;
+  return unless @{$self};
+  return CORE::pop(@{$self}); ## Make clear we are using the core pop method
+}
+
+sub top {
+  my $self = shift;
+  return unless @{$self};
+  return $self->[-1];
+}
+
+sub min {
+  my $self = shift;
+  return unless @{$self};
+  my $min = $self->[0];
+  foreach (@{$self}) {
+    $min = $_ if $_ < $min;
+  }
+  return $min;
+}
+
+1;
diff --git a/challenge-095/james-smith/perl/ch-1.pl b/challenge-095/james-smith/perl/ch-1.pl
new file mode 100644
index 0000000000..921ddaec2b
--- /dev/null
+++ b/challenge-095/james-smith/perl/ch-1.pl
@@ -0,0 +1,50 @@
+#!/usr/local/bin/perl
+
+use strict;
+
+use warnings;
+use feature qw(say);
+use Test::More;
+
+is( is_palindrome_rev(1221), 1 ); ## Even number of digits
+is( is_palindrome_rev(-101), 0 ); ## -ve number
+is( is_palindrome_rev(101),  1 ); ## Odd number of digits
+is( is_palindrome_rev(90),   0 ); ## Not-palindromic
+
+is( is_palindrome_array(1221), 1 );
+is( is_palindrome_array(-101), 0 );
+is( is_palindrome_array(101),  1 );
+is( is_palindrome_array(90),   0 );
+
+done_testing();
+
+## I will provide two solutions here...
+
+## (1) The first one just treating the two numbers as strings and
+##      using reverse
+
+sub is_palindrome_rev {
+  return ( $_[0] eq reverse $_[0]) ? 1 : 0;
+}
+
+## (2) The second one just treating the two numbers as numbers and
+##     using the % operator to split them into digits.
+##     Notes:
+##      * Push is more optimal than unshift - so the digit list I get
+##        is in reverse order but that doesn't matter in this case
+##      * Obviously -ve numbers will fail so deal with this first
+##      * When the digits array has one element then we know the
+##        remaining digits form a palindrome {we can't use the
+##        shift/pop trick as it will compare digit with undef;
+
+sub is_palindrome_array {
+  my $n = shift;
+  return 0 if $n < 0;
+  my @digits  = $n%10;
+  push @digits, $n%10 while $n = int ($n/10);
+  while( @digits>1 ) {
+    return 0 if shift @digits != pop @digits;
+  }
+  return 1;
+}
+
diff --git a/challenge-095/james-smith/perl/ch-2.pl b/challenge-095/james-smith/perl/ch-2.pl
new file mode 100644
index 0000000000..f953417ba7
--- /dev/null
+++ b/challenge-095/james-smith/perl/ch-2.pl
@@ -0,0 +1,28 @@
+#!/usr/local/bin/perl
+
+use strict;
+
+use warnings;
+use feature qw(say);
+use Test::More;
+use lib q(.);
+use Stack;
+
+## Look at the Stack module for implementation
+
+#                        return value  stack after op
+my $stack = Stack->new;    # $stack    [          ]
+$stack->push(2);           # $stack    [ 2        ]
+$stack->push(-1);          # $stack    [ 2, -1    ]
+$stack->push(0);           # $stack    [ 2, -1, 0 ]
+$stack->pop;               # 0         [ 2, -1    ]
+is( $stack->top, -1 );     # -1        [ 2, -1    ]
+$stack->push(0);           # $stack    [ 2, -1, 0 ]
+is( $stack->min, -1 );     # -1        [ 2, -1, 0 ]
+$stack->pop;               # 0         [ 2, -1    ]
+$stack->pop;               # -1        [ 2        ]
+is( $stack->pop, 2 );      # 2         [          ]
+is( $stack->top, undef );  # undef     [          ]
+
+done_testing();
+