Data update

Task/Pancake-numbers/Perl/pancake-numbers.pl

@@ -1,43 +1,23 @@
-use strict;
+#!/usr/bin/perl
+
+use strict; # https://rosettacode.org/wiki/Pancake_numbers
 use warnings;
-use feature 'say';
 
-sub pancake {
-    my($n) = @_;
-    my ($gap, $sum, $adj) = (2, 2, -1);
-    while ($sum < $n) { $sum += $gap = $gap * 2 - 1 and $adj++ }
-    $n + $adj;
-}
-
-my $out;
-$out .= sprintf "p(%2d) = %2d ", $_, pancake $_ for 1..20;
-say $out =~ s/.{1,55}\K /\n/gr;
-
-# Maximum number of flips plus examples using exhaustive search
-sub pancake2 {
-    my ($n) = @_;
-    my $numStacks = 1;
-    my @goalStack = 1 .. $n;
-    my %newStacks = my %stacks = (join(' ',@goalStack), 0);
-    for my $k (1..1000) {
-        my %nextStacks;
-        for my $pos (2..$n) {
-            for my $key (keys %newStacks) {
-                my @arr = split ' ', $key;
-                my $cakes = join ' ', (reverse @arr[0..$pos-1]), @arr[$pos..$#arr];
-                $nextStacks{$cakes} = $k unless $stacks{$cakes};
-            }
-        }
-        %stacks = (%stacks, (%newStacks = %nextStacks));
-        my $perms    = scalar %stacks;
-        my %inverted = reverse %stacks;
-        return $k-1, $inverted{(sort keys %inverted)[-1]} if $perms == $numStacks;
-        $numStacks = $perms;
-   }
-}
-
-say "\nThe maximum number of flips to sort a given number of elements is:";
-for my $n (1..9) {
-    my ($a,$b) = pancake2($n);
-    say "pancake($n) = $a example: $b";
-}
+for my $n ( 1 .. 9 )
+  {
+  my @queue = my $last = join '', map chr 96 + $_, 1 .. $n;
+  my %seen = ($last => '');
+  while( @queue )
+    {
+    my ($stack, @flips) = split ' ', shift @queue;
+    for my $flip ( 2 .. $n )
+      {
+      my $new = (reverse substr $stack, 0, $flip) . substr $stack, $flip;
+      defined $seen{$new} or
+        push @queue, $last = $seen{$new} = "$new $flip @flips";
+      }
+    }
+  my ($stack, @flips) = split ' ', $last;
+  printf "%9s  ", $stack;
+  printf "size %d  score: %2d  flip the top %s\n", $n, @flips + 0, "@flips";
+  }