P13 - Run-length encoding of a list (direct solution).
AUTHOR
Philip Potter
We use gather as a loop modifier, to gather a list over all the loop
iterations
Specification
P13 (**) Run-length encoding of a list (direct solution).
Implement the so-called run-length encoding data compression method
directly. I.e. don't explicitly create the sublists containing the
duplicates, as in problem P09, but only count them. As in problem P11,
simplify the result list by replacing the singletons [1,X] by X.
Example
> encode_direct(<a a a a b c c a a d e e e e>).perl.say
([4, "a"], "b", [2, "c"], [2, "a"], "d", [4, "e"])
use v6;
sub runlength (@a) {
gather {
last if [email protected];
my $val = @a.shift;
my $num = 1;
while @a[0] ~~ $val { @a.shift; $num++; }
take $num == 1 ?? $val !! [$num,$val];
}
}
my @l = <a a a a b c c a a d e e e e>;
say ~@l;
runlength(@l).list.perl.say;
# vim: expandtab shiftwidth=4 ft=perl6