2 files changed, 141 insertions, 0 deletions
diff --git a/ch-1.pl b/ch-1.pl
new file mode 100644
index 0000000000..3b06d8127f
--- /dev/null
+++ b/ch-1.pl
@@ -0,0 +1,92 @@
+#!/usr/bin/perl
+use strict;
+use Data::Dumper;
+
+my @ro_tree1;
+
+sub array_transform_rowform {
+
+    my ($h, $val, @kids) = @_;
+    if (! defined(@ro_tree1[$h])) {    
+        @{$ro_tree1[$h]} = ();
+    }
+    push @{$ro_tree1[$h]}, $val; 
+
+    if ($kids[0]) {
+        my ($temp, @smallkids) = @{kids[0]};
+        array_transform_rowform($h+1, shift @{$kids[0]}, @{$kids[0]});
+    } 
+    if ($kids[1]) {
+        my ($temp, @smallkids) = @{kids[1]};
+        array_transform_rowform($h+1, shift @{$kids[1]}, @{$kids[1]});
+    }
+
+}
+
+sub rowform_transform_array {
+    my @rowform = @_;
+    my $height = $#rowform;
+    my @data = ();
+    for (0..2**$height-1) { push @data, [ $rowform[$height][$_] ];  }
+    for my $i (reverse 1..$height-1) {
+        my @newdata = ();
+        for my $j (0..2**$i-1) {
+            $newdata[$j] = CombineTwo($data[$j*2], $data[$j*2+1]);
+            unshift @{$newdata[$j]}, $rowform[$i][$j];
+        }
+        for my $j (0..2**$i-1) {$data[$j] = $newdata[$j];}
+    }
+
+    return [$rowform[0][0], $data[0], $data[1]] ;
+}
+
+sub CombineTwo {
+    my @temp = ($_[0], $_[1]);
+    return \@temp;
+}
+
+sub swaprowformtree {
+    my @btree = @_;
+    my $N = $#btree;
+    for my $i (1..$N) {
+        for my $j (0..2**($i-1)-1) {
+            ($btree[$i][$j], $btree[$i][2**($i)-1-$j])
+            = ($btree[$i][2**($i)-1-$j], $btree[$i][$j]);
+        }
+    }
+
+    return @btree;
+}
+
+# ===================================================
+
+my $tree1 = [2, [3, [5], [7]], [11, [13], [17]] ] ; 
+#SAMPLE INPUT (nested array form)
+
+array_transform_rowform(0, shift @{$tree1}, @{$tree1});
+
+$Data::Dumper::Terse = 1; 
+$Data::Dumper::Indent = 0;
+
+print Dumper rowform_transform_array swaprowformtree @ro_tree1;
+
+# ===================================================
+
+# REFERENCES (format of binary tree): 
+# https://ry.ca/2020/04/path-sum/
+# https://raku-musings.com/diff-sum.html
+# http://blogs.perl.org/users/laurent_r/2020/04/perl-weekly-challenge-56-diff-k-and-path-sum.html
+
+
+sub display_rowform {       # haven't used in program; use for checking
+    my @bb = @_;
+    print "(";
+    for my $i (0..$#bb) {
+        print "[";
+        print join "," , @{$bb[$i]};
+        print "],\n"
+    }
+
+    print ")";
+}
+
diff --git a/ch-2.pl b/ch-2.pl
new file mode 100644
index 0000000000..2d628176b3
--- /dev/null
+++ b/ch-2.pl
@@ -0,0 +1,49 @@
+#!/usr/bin/perl
+use strict;
+use Scalar::Util qw/dualvar/;
+
+#Usage: $   ch-2.pl [list of words]
+#e.g. ch-2.pl alphabet book carpet cadmium cadeau alpine
+#output: alph , b , car , cadm , cade , alpi
+
+my @data = @ARGV;
+
+
+
+my $N = $#data + 1;
+
+my $i = 0; 
+my @dualv_sorted = sort {$a cmp $b} map { dualvar($i++, $_) } @data;
+
+my @dualv_processed = ();
+
+my $k = 1;
+
+for (0..$N-2) {
+    my $tempk = $k;
+    $k = 1;
+    my $first = substr($dualv_sorted[$_], 0, $k); 
+  
+    while ($first eq substr( $dualv_sorted[$_+1], 0, $k)) {
+        $k++;
+        $first = substr( $dualv_sorted[$_], 0, $k);
+    }
+
+    $first = substr($dualv_sorted[$_], 0, max($tempk, $k));
+    $dualv_processed[$_] =  dualvar( $dualv_sorted[$_]+0 , "$first");
+}
+
+
+   $dualv_processed[$N-1] 
+ = dualvar($dualv_sorted[$N-1]+0, substr($dualv_sorted[$N-1], 0, $k));
+
+
+print join " , ", (sort {$a <=> $b} @dualv_processed);
+
+
+
+
+
+sub max {
+    return ($_[0] > $_[1] ? $_[0]: $_[1]); 
+}