3 files changed, 153 insertions, 0 deletions
diff --git a/challenge-059/cheok-yin-fung/BLOG.txt b/challenge-059/cheok-yin-fung/BLOG.txt
new file mode 100644
index 0000000000..0db37b7d91
--- /dev/null
+++ b/challenge-059/cheok-yin-fung/BLOG.txt
@@ -0,0 +1 @@
+http://blogs.perl.org/users/c_y_fung/2020/05/cys-take-on-perl-weekly-challenge-059.html
diff --git a/challenge-059/cheok-yin-fung/perl/ch-1.pl b/challenge-059/cheok-yin-fung/perl/ch-1.pl
new file mode 100644
index 0000000000..64e34adbb2
--- /dev/null
+++ b/challenge-059/cheok-yin-fung/perl/ch-1.pl
@@ -0,0 +1,121 @@
+#!/usr/bin/perl
+use strict;
+
+{ package item;
+
+    sub new
+    {
+        my ($class) = @_;
+        bless {
+            _value => $_[1],
+            _next => $_[2],
+        }, $class;
+    }
+
+    sub value { $_[0]->{_value}}
+
+    sub inext {
+        my ($self, $newnext) = @_;
+        $self->{_next} = $newnext if defined($newnext);
+        return $self->{_next};
+    }
+
+    sub unlink {
+        my ($self) = @_;
+        $self->{_next} = undef;
+        return $self->{_next};
+    }
+}
+
+#my @input = (2,1, 2,3);
+#my $K = 2;
+
+my @input = (5,6,3,2,7,9);
+my $K = 6;
+
+#my @input = (1 , 4, 3, 2, 5, 2 );
+#my $K = 3;
+
+# my @input = (2 , 4, 3, 1, 5, 1 );
+ #  my $K = 3;
+
+my ($head, $smallpivot, $inusepivot);
+my $ll;
+
+
+sub make_linked_list {
+    my @temp_list = @_;
+    $ll->[$#temp_list] = item->new( $temp_list[$#temp_list] , \(undef) );
+    for (reverse 0..$#temp_list-1) {
+        $ll->[$_] = item->new($temp_list[$_] , \( $ll->[$_+1] ) ); 
+    }
+    $head = \($ll->[0]);
+}
+
+
+
+my $HELPER = -1;
+make_linked_list($HELPER, @input);
+
+$smallpivot = $head;
+$inusepivot = ${$head}->inext;
+
+sub print_linked_listi {   #for testing use 
+    my $i = 0;
+    my $t = ${$head};
+    while( $t = ${$t->inext} and $i<10) {
+        print $t->value, "->";
+        $i++;
+    }
+    print "nil\n";
+}
+
+sub print_linked_list {
+    my $t = ${$head};
+    while( $t = ${$t->inext} ) {
+        print $t->value, "->";
+    }
+    print "nil\n";
+}
+
+
+print "\nbefore: ";
+print_linked_list;
+print "\n";
+
+my $j = 0;
+
+my $previous = $head;
+while( 1) {  #j is for testing help  
+
+    #    print $$inusepivot->value, " " ,$$smallpivot->value, " \n"; 
+    # print_linked_list;print "\n";
+
+    if ($$inusepivot->value < $K) {
+        $$previous->unlink;
+        $$previous->inext( $$inusepivot->inext );
+
+        $$inusepivot->unlink;
+        $$inusepivot->inext($$smallpivot->inext);
+        
+        $$smallpivot->unlink;
+        $$smallpivot->inext($inusepivot);
+        $smallpivot = $inusepivot;
+
+    }
+
+
+    if (($$previous->inext != \undef) and ($$inusepivot->inext != \undef)) {
+        $previous = $inusepivot;
+        $inusepivot = $$inusepivot->inext;
+    }
+    else {
+        print "\nafter : ";
+        print_linked_list;
+        exit;
+    }
+
+}
+
+
+
diff --git a/challenge-059/cheok-yin-fung/perl/ch-2.pl b/challenge-059/cheok-yin-fung/perl/ch-2.pl
new file mode 100644
index 0000000000..420c20d172
--- /dev/null
+++ b/challenge-059/cheok-yin-fung/perl/ch-2.pl
@@ -0,0 +1,31 @@
+#!/usr/bin/perl
+use strict;
+use Test::Simple tests => 2;
+use List::Util qw/max sum/;
+
+#reference: https://www.tutorialspoint.com/perl/bitwise_operators_example.htm
+
+
+sub f {  # compare two bit-strings by xor
+    my $hint = ($_[0] ^ $_[1]) ;
+    my $ans = sum (split //, sprintf("%b", $hint));
+    return $ans;  
+}
+
+# first parameter: number of terms; remaining: terms in the list
+sub conclude {
+    my ($N, @val) = @_; 
+    my $sum = 0;
+    for my $i (0..$N-2) {
+       for my $j ($i+1..$N-1) {
+          $sum += f($val[$i], $val[$j]); 
+       }
+    }
+    return $sum; 
+}
+
+
+ok (conclude(3,2,3,4) == 6), "bad";
+ok (conclude(2,1,3)==1), "too bad";
+
+