From 0b86f89009795ee7606421f61ad9bed82d45b0d7 Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Mon, 25 Jan 2021 08:58:44 +0000
Subject: challenge 97

---
 challenge-097/james-smith/perl/ch-1.pl | 17 +++++++++++++++++
 challenge-097/james-smith/perl/ch-2.pl | 29 +++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 challenge-097/james-smith/perl/ch-1.pl
 create mode 100644 challenge-097/james-smith/perl/ch-2.pl

diff --git a/challenge-097/james-smith/perl/ch-1.pl b/challenge-097/james-smith/perl/ch-1.pl
new file mode 100644
index 0000000000..d6dfd58a56
--- /dev/null
+++ b/challenge-097/james-smith/perl/ch-1.pl
@@ -0,0 +1,17 @@
+#!/usr/local/bin/perl
+
+use strict;
+
+use warnings;
+use feature qw(say);
+use Test::More;
+
+is( caesar('ABCDEFGHIJKLMNOPQRSTUVWXYZ',3), 'XYZABCDEFGHIJKLMNOPQRSTUVW' );
+is( caesar('THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG',3), 'QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD' );
+
+done_testing();
+
+sub caesar {
+  return join q(), map { m{[A-Z]} ? chr 65+(ord($_)-65-$_[1])%26 : $_ } split m{}, $_[0];
+}
+
diff --git a/challenge-097/james-smith/perl/ch-2.pl b/challenge-097/james-smith/perl/ch-2.pl
new file mode 100644
index 0000000000..26bdfe22a1
--- /dev/null
+++ b/challenge-097/james-smith/perl/ch-2.pl
@@ -0,0 +1,29 @@
+#!/usr/local/bin/perl
+
+use strict;
+
+use warnings;
+use feature qw(say);
+use Test::More;
+
+is( min_flips('101100101',3), 1 );
+is( min_flips('10110111', 4), 2 );
+is( min_flips('101100100',4), 1 );
+is( min_flips('0000000100100011010001010110011110001001101010111100110111101111',4), 32 );
+
+done_testing();
+
+sub min_flips {
+  my( $str, $n, @parts ) = @_;;
+  my $min = length $str;
+  push @parts, substr $str,0,$n,'' while length $str;
+  foreach my $r (@parts) {
+    my $t = 0;
+    foreach my $s (@parts) {
+      $t += ($s^$r) =~ tr/\x01/\x01/;
+    }
+    $min = $t if $t < $min;
+  }
+  return $min;
+}
+
-- 
cgit 


From c4a60d0ec86e18c9ec046f7f341b41bb747e61fd Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Mon, 25 Jan 2021 14:50:16 +0000
Subject: remove the for loops and make this a map list....

---
 challenge-097/james-smith/perl/ch-2.pl | 50 ++++++++++++++++++++++++++--------
 1 file changed, 38 insertions(+), 12 deletions(-)

diff --git a/challenge-097/james-smith/perl/ch-2.pl b/challenge-097/james-smith/perl/ch-2.pl
index 26bdfe22a1..9df291a034 100644
--- a/challenge-097/james-smith/perl/ch-2.pl
+++ b/challenge-097/james-smith/perl/ch-2.pl
@@ -8,22 +8,48 @@ use Test::More;
 
 is( min_flips('101100101',3), 1 );
 is( min_flips('10110111', 4), 2 );
-is( min_flips('101100100',4), 1 );
+is( min_flips('101100100',3), 1 );
 is( min_flips('0000000100100011010001010110011110001001101010111100110111101111',4), 32 );
 
+use Data::Dumper;
+
 done_testing();
 
 sub min_flips {
-  my( $str, $n, @parts ) = @_;;
-  my $min = length $str;
-  push @parts, substr $str,0,$n,'' while length $str;
-  foreach my $r (@parts) {
-    my $t = 0;
-    foreach my $s (@parts) {
-      $t += ($s^$r) =~ tr/\x01/\x01/;
-    }
-    $min = $t if $t < $min;
-  }
-  return $min;
+  ## Golf mode on...
+  return [
+    map { local $/ =
+            local $\ = ( $_[0] ^ ( substr $_[0], $_, $_[1]) x (length($_[0])/$_[1]) ) =~ tr/\x01/\x01/,
+            !$_ || $_ < $/ ? $\ : $/,
+        }
+    map { $_*$_[1] }
+    0 .. (length($_[0])/$_[1]-1)
+  ]->[-1];
+  ## We could use variales here - but playing with localised special variables is fun!
+  ## $/ <- minimum value
+  ## $\ <- value for given chunk....
+  ##
+  ## The inner map + range combination returns a list of ids of the form 0, $n, 2*$n until the
+  ## end of the array, we use this to chunk the array up for comparison
+  ##
+  ## Inside the end map - we first string "xor" the string with the repeated chunk of the array.
+  ## so e.g. for the first example this becomes:
+  ##   '101100101' ^ '101'.'101'.'101'
+  ##   '101100101' ^ '100'.'100'.'100'
+  ##   '101100101' ^ '101'.'101'.'101'
+  ## if the symbols match you get a value \x00, when they don't match you get value \x01
+  ## so we then count the \x01's using tr... and store in $\
+  ##
+  ## Next if it is the first chunk OR the value of $\ is less than the current min ($/)
+  ## We set $/ to $\ otherwise we leave it as $/
+  ##
+  ## The resultant array consists of the running minimum in the examples
+  ## for ex 1: it is [1,1,1]
+  ## for ex 2: it is [1,1]
+  ## for ex 3: it is [2,1,1]
+  ##
+  ## We need the last value of this so we wrap the list into an array ref and take the last element
+  ##
+  ## [ list... ]->[-1];
 }
 
-- 
cgit 


From 071408de692b446843bdc102d5b71acea69cfc92 Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Mon, 25 Jan 2021 15:24:12 +0000
Subject: golfed

---
 challenge-097/james-smith/perl/ch-2.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/challenge-097/james-smith/perl/ch-2.pl b/challenge-097/james-smith/perl/ch-2.pl
index 9df291a034..a995d64d5c 100644
--- a/challenge-097/james-smith/perl/ch-2.pl
+++ b/challenge-097/james-smith/perl/ch-2.pl
@@ -23,7 +23,7 @@ sub min_flips {
             !$_ || $_ < $/ ? $\ : $/,
         }
     map { $_*$_[1] }
-    0 .. (length($_[0])/$_[1]-1)
+    0 .. ( length($_[0])/$_[1] - 1 )
   ]->[-1];
   ## We could use variales here - but playing with localised special variables is fun!
   ## $/ <- minimum value
-- 
cgit 


From 87f2cca1c08b724332092b0ab73fcd522247af53 Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Mon, 25 Jan 2021 15:36:23 +0000
Subject: added some comments

---
 challenge-097/james-smith/perl/ch-2.pl | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/challenge-097/james-smith/perl/ch-2.pl b/challenge-097/james-smith/perl/ch-2.pl
index a995d64d5c..805b834d72 100644
--- a/challenge-097/james-smith/perl/ch-2.pl
+++ b/challenge-097/james-smith/perl/ch-2.pl
@@ -17,11 +17,19 @@ done_testing();
 
 sub min_flips {
   ## Golf mode on...
+  ##
+  ## This was to use this to serve as an example of perl idioms that other programmers
+  ## may find it difficult to understand - and so I tried to put as many of them in relatively
+  ## short function....
+  ##
+  ## One statement functions are a lovely perl concept - even if they can get a bit difficult
+  ## to read....
+  ##
   return [
     map { local $/ =
-            local $\ = ( $_[0] ^ ( substr $_[0], $_, $_[1]) x (length($_[0])/$_[1]) ) =~ tr/\x01/\x01/,
-            !$_ || $_ < $/ ? $\ : $/,
-        }
+      local $\ = ( $_[0] ^ ( substr $_[0], $_, $_[1]) x (length($_[0])/$_[1]) ) =~ tr/\x01/\x01/,
+      !$_ || $_ < $/ ? $\ : $/,
+    }
     map { $_*$_[1] }
     0 .. ( length($_[0])/$_[1] - 1 )
   ]->[-1];
-- 
cgit 


From 79dc1dd47f6301db6742e3c1cc63f9a129ad9137 Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Mon, 25 Jan 2021 15:36:37 +0000
Subject: added some comments

---
 challenge-097/james-smith/perl/ch-2.pl | 2 --
 1 file changed, 2 deletions(-)

diff --git a/challenge-097/james-smith/perl/ch-2.pl b/challenge-097/james-smith/perl/ch-2.pl
index 805b834d72..42b107ffb7 100644
--- a/challenge-097/james-smith/perl/ch-2.pl
+++ b/challenge-097/james-smith/perl/ch-2.pl
@@ -11,8 +11,6 @@ is( min_flips('10110111', 4), 2 );
 is( min_flips('101100100',3), 1 );
 is( min_flips('0000000100100011010001010110011110001001101010111100110111101111',4), 32 );
 
-use Data::Dumper;
-
 done_testing();
 
 sub min_flips {
-- 
cgit 


From c0afb079eb7a7b59ee64caedef57208c63d25777 Mon Sep 17 00:00:00 2001
From: drbaggy <js5@sanger.ac.uk>
Date: Mon, 25 Jan 2021 16:22:15 +0000
Subject: tidied up

---
 challenge-097/james-smith/perl/ch-2.pl | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/challenge-097/james-smith/perl/ch-2.pl b/challenge-097/james-smith/perl/ch-2.pl
index 42b107ffb7..81f89d7e4f 100644
--- a/challenge-097/james-smith/perl/ch-2.pl
+++ b/challenge-097/james-smith/perl/ch-2.pl
@@ -6,9 +6,11 @@ use warnings;
 use feature qw(say);
 use Test::More;
 
+is( min_flips('101101',3), 0 );
 is( min_flips('101100101',3), 1 );
 is( min_flips('10110111', 4), 2 );
-is( min_flips('101100100',3), 1 );
+is( min_flips('100101100',3), 1 );
+is( min_flips('101100100100101',3), 2 );
 is( min_flips('0000000100100011010001010110011110001001101010111100110111101111',4), 32 );
 
 done_testing();
@@ -23,10 +25,12 @@ sub min_flips {
   ## One statement functions are a lovely perl concept - even if they can get a bit difficult
   ## to read....
   ##
+
+  local $/;
   return [
-    map { local $/ =
-      local $\ = ( $_[0] ^ ( substr $_[0], $_, $_[1]) x (length($_[0])/$_[1]) ) =~ tr/\x01/\x01/,
-      !$_ || $_ < $/ ? $\ : $/,
+    map {
+      local $\ = ( $_[0] ^ (substr$_[0],$_,$_[1]) x (length($_[0])/$_[1]) ) =~ tr/\x01/\x01/,
+      $/ = (!$_ || ($\ < $/)) ? $\ : $/
     }
     map { $_*$_[1] }
     0 .. ( length($_[0])/$_[1] - 1 )
@@ -49,10 +53,13 @@ sub min_flips {
   ## Next if it is the first chunk OR the value of $\ is less than the current min ($/)
   ## We set $/ to $\ otherwise we leave it as $/
   ##
-  ## The resultant array consists of the running minimum in the examples
-  ## for ex 1: it is [1,1,1]
-  ## for ex 2: it is [1,1]
-  ## for ex 3: it is [2,1,1]
+  ## The resulting array consists of the value for the node and the running minimum in the examples
+  ##
+  ## for ex 1: it is [0,0,0,0]
+  ## for ex 2: it is [1,1,2,1,1,1]
+  ## for ex 3: it is [1,1,1,1]
+  ## for ex 4: it is [2,2,2,2]
+  ## for ex 5: it is [2,2,1,1,1,1]
   ##
   ## We need the last value of this so we wrap the list into an array ref and take the last element
   ##
-- 
cgit