From 746cf884930fc15574fa75bd5377cb95ed85fc17 Mon Sep 17 00:00:00 2001
From: Stephen Lynn <bizlsg@localhost.localdomain>
Date: Wed, 27 Dec 2023 06:47:41 +0800
Subject: pwc 249

---
 challenge-249/steve-g-lynn/blog.txt     |  1 +
 challenge-249/steve-g-lynn/perl/ch-1.pl | 44 +++++++++++++++++++++++++++++++++
 challenge-249/steve-g-lynn/perl/ch-2.pl | 30 ++++++++++++++++++++++
 3 files changed, 75 insertions(+)
 create mode 100644 challenge-249/steve-g-lynn/blog.txt
 create mode 100755 challenge-249/steve-g-lynn/perl/ch-1.pl
 create mode 100755 challenge-249/steve-g-lynn/perl/ch-2.pl

diff --git a/challenge-249/steve-g-lynn/blog.txt b/challenge-249/steve-g-lynn/blog.txt
new file mode 100644
index 0000000000..393fdab0ae
--- /dev/null
+++ b/challenge-249/steve-g-lynn/blog.txt
@@ -0,0 +1 @@
+https://thiujiac.blogspot.com/2023/12/pwc-249.html
diff --git a/challenge-249/steve-g-lynn/perl/ch-1.pl b/challenge-249/steve-g-lynn/perl/ch-1.pl
new file mode 100755
index 0000000000..b15d537721
--- /dev/null
+++ b/challenge-249/steve-g-lynn/perl/ch-1.pl
@@ -0,0 +1,44 @@
+#!/usr/bin/env -S perl -wl
+
+use Data::Dumper qw(Dumper);
+
+local *equal_pairs = sub {
+    #-- return () if input is of odd length
+    ((scalar(@_) % 2) > 0) && (return ());
+    
+    #-- count number of occurrences of each element using a hash
+    local %_ = ();
+    map {$_{$_}++} @_;
+    
+    #-- if any element occurs an odd number of times, return ()
+    (grep {($_{$_} % 2) > 0} keys %_) && (return ());
+    
+    #-- loop thru %_ keys, returning pairs of such keys
+    map {
+        my $k=$_; 
+        my $num_pairs=( ($_{$k}) / 2 );
+        map {
+            [$k, $k]
+        } 1 .. $num_pairs;    
+    } 
+    keys %_;    
+};
+
+print Dumper &equal_pairs(3,2,3,2,2,2);
+#$VAR1 = [
+#          '3',
+#          '3'
+#        ];
+#$VAR2 = [
+#          '2',
+#          '2'
+#        ];
+#$VAR3 = [
+#          '2',
+#          '2'
+#        ];
+
+print Dumper &equal_pairs(1,2,3,4);
+# no printed output (empty array)
+
+1;
diff --git a/challenge-249/steve-g-lynn/perl/ch-2.pl b/challenge-249/steve-g-lynn/perl/ch-2.pl
new file mode 100755
index 0000000000..5f64069776
--- /dev/null
+++ b/challenge-249/steve-g-lynn/perl/ch-2.pl
@@ -0,0 +1,30 @@
+#!/usr/bin/env -S perl -wl
+
+local *DI_string_match = sub {
+    my $str = $_[0];
+    
+    #-- return 0 (error) if input is not D or I only
+    ($str =~ /^[DI]+$/) || (return 0);
+
+    #-- create sorted array of indices from which to generate output
+    my @tmp=(0 .. length($str));
+    
+    #-- loop through $str indices, 
+    # if a position i is 'D' pop @tmp (highest item) and assign to retval[i]
+    # if a position i is 'I' shift @tmp (lowest item) and assign to retval[i]
+
+    my @retval = (); #-- return value
+    map {
+        (substr($str,$_,1) eq 'D') && ($retval[$_] = pop @tmp);
+        (substr($str,$_,1) eq 'I') && ($retval[$_] = shift @tmp);
+    }
+    0 .. length($str)-1;
+    $retval[length($str)] = shift @tmp; #-- last item left
+    @retval;
+};
+
+print join ',',  &DI_string_match('IDID'); #0,4,1,3,2
+print join ',',  &DI_string_match('III'); #0,1,2,3
+print join ',',  &DI_string_match('DDI'); #3,2,0,1
+
+1;
-- 
cgit 


From 09ffbd5e40441c537d3550f0040558e5756f9d79 Mon Sep 17 00:00:00 2001
From: Stephen Lynn <bizlsg@localhost.localdomain>
Date: Wed, 27 Dec 2023 07:06:24 +0800
Subject: ch-2 improved

---
 challenge-249/steve-g-lynn/perl/ch-2.pl | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/challenge-249/steve-g-lynn/perl/ch-2.pl b/challenge-249/steve-g-lynn/perl/ch-2.pl
index 5f64069776..37d26f55fd 100755
--- a/challenge-249/steve-g-lynn/perl/ch-2.pl
+++ b/challenge-249/steve-g-lynn/perl/ch-2.pl
@@ -6,20 +6,21 @@ local *DI_string_match = sub {
     #-- return 0 (error) if input is not D or I only
     ($str =~ /^[DI]+$/) || (return 0);
 
-    #-- create sorted array of indices from which to generate output
-    my @tmp=(0 .. length($str));
+    #-- create mutable temp vars containing highest and lowest indices
+    my ($lowest,$highest)=(0, length($str));
     
     #-- loop through $str indices, 
-    # if a position i is 'D' pop @tmp (highest item) and assign to retval[i]
-    # if a position i is 'I' shift @tmp (lowest item) and assign to retval[i]
+    # if str[i] is 'D', assign highest in output[i] and decrement it
+    # if a position i is 'I', assign lowest in output[i] and increment it
 
     my @retval = (); #-- return value
     map {
-        (substr($str,$_,1) eq 'D') && ($retval[$_] = pop @tmp);
-        (substr($str,$_,1) eq 'I') && ($retval[$_] = shift @tmp);
+        (substr($str,$_,1) eq 'D') && ($retval[$_] = $highest--);
+        (substr($str,$_,1) eq 'I') && ($retval[$_] = $lowest++);
     }
     0 .. length($str)-1;
-    $retval[length($str)] = shift @tmp; #-- last item left
+    ($lowest==$highest) || die "Something wrong ...$!";
+    $retval[length($str)] = $highest; #-- last item left
     @retval;
 };
 
-- 
cgit 


From 292ffcd983dd4232331dd60dad3e98eff6a4de7e Mon Sep 17 00:00:00 2001
From: Stephen Lynn <bizlsg@localhost.localdomain>
Date: Wed, 27 Dec 2023 08:24:07 +0800
Subject: ch-2 improvement

---
 challenge-249/steve-g-lynn/perl/ch-2.pl | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/challenge-249/steve-g-lynn/perl/ch-2.pl b/challenge-249/steve-g-lynn/perl/ch-2.pl
index 37d26f55fd..b81273d592 100755
--- a/challenge-249/steve-g-lynn/perl/ch-2.pl
+++ b/challenge-249/steve-g-lynn/perl/ch-2.pl
@@ -11,12 +11,13 @@ local *DI_string_match = sub {
     
     #-- loop through $str indices, 
     # if str[i] is 'D', assign highest in output[i] and decrement it
-    # if a position i is 'I', assign lowest in output[i] and increment it
+    # if str[i] is 'I', assign lowest in output[i] and increment it
 
     my @retval = (); #-- return value
     map {
-        (substr($str,$_,1) eq 'D') && ($retval[$_] = $highest--);
-        (substr($str,$_,1) eq 'I') && ($retval[$_] = $lowest++);
+        (substr($str,$_,1) eq 'D') ?
+        ($retval[$_] = $highest--) :
+        ($retval[$_] = $lowest++);
     }
     0 .. length($str)-1;
     ($lowest==$highest) || die "Something wrong ...$!";
-- 
cgit