1 files changed, 35 insertions, 14 deletions
diff --git a/challenge-060/mark-anderson/raku/ch-1.raku b/challenge-060/mark-anderson/raku/ch-1.raku
index 5ad393a053..c8d3b23d61 100644
--- a/challenge-060/mark-anderson/raku/ch-1.raku
+++ b/challenge-060/mark-anderson/raku/ch-1.raku
@@ -1,25 +1,46 @@
 #!/usr/bin/env raku
 
-my %letter;
-my %number;
+sub from-excel(Str $str) {
+    my $num;
 
-my $number = 1;
-my $letter = "A";
+    my @letters = $str.comb;
 
-loop {
-    last if $number > 16384;
+    my $exp = @letters.keys.max;
 
-    %letter{$number} = $letter;
-    %number{$letter} = $number;
+    for @letters {
+        $num += ($_.ord - 64) * (26 ** $exp--);
+    }    
 
-    $number++;
-    $letter++;
+    $num;
 }
 
-multi sub MAIN (Str $str where $str.all ~~ /<[A..Z]>/) {
-    say %number{$str};
+sub to-excel(UInt $num is copy) {
+    my $string;
+    my $quotient;
+    my $remainder;
+    my @letters = ("A" .. "Z");
+
+    while $num > 26 {
+        $quotient = ($num / 26).Int;
+        $remainder = $num % 26;
+    
+        if $remainder == 0 {
+            $quotient--;
+            $remainder = 26;
+        }
+
+        $string ~= @letters[$remainder - 1];
+        $num = $quotient;
+    }
+
+    $string ~= @letters[$num - 1];
+    $string.flip;
+}
+
+multi sub MAIN (Str $str where $str ~~ /^<[A..Z]>+$/) {
+    say from-excel($str);
 }
 
-multi sub MAIN (UInt $num where $num <= 16384) {
-    say %letter{$num};
+multi sub MAIN (UInt $num where $num > 0) {
+    say to-excel($num);
 }