Best shuffle: Difference between revisions

{{works with|Rakudo Star|2010.12}}

{{incorrect|Perl 6| See [[Talk:Best_shuffle#Perl_6|Perl 6]] in talk page.}}

<lang perl6>sub best-shuffle (Str $s) {

my @orig = $s.comb;

my @pos;

# Fill @pos with positions in the order that we want to fill

# them. (Once Rakudo has &roundrobin, this will be doable in

# one statement.)

{

my %pos = classify { @orig[$^i] }, keys @orig;

my @k = map *.key, sort *.value.elems, %pos;

while %pos {

for @k -> $letter {

%pos{$letter} or next;

push @pos, %pos{$letter}.pop;

%pos{$letter}.elems or %pos.delete: $letter;

@pos .= reverse;

my @letters = @orig;

my @new = Any xx $s.chars;

# Now fill in @new with @letters according to each position

# in @pos, but skip ahead in @letters if we can avoid

# matching characters that way.

while @letters {

my ($i, $p) = 0, shift @pos;

++$i while @letters[$i] eq @orig[$p] and $i < @letters.end;

@new[$p] = splice @letters, $i, 1;

my $score = elems grep ?*, map * eq *, do @new Z @orig;

@new.join, $score;