Run-length encoding: Difference between revisions
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12W1B12W3B24W1B14W
WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW</pre>
=={{header|SparForte}}==
Line 5,576 ⟶ 5,522:
? from_rle( "12W1B12W3B24W1B14W");
end rle;</syntaxhighlight>
=={{header|SQL}}==
{{works with|PL/pgSQL}}
<br>
* RLE encoding
<syntaxhighlight lang="sql">
-- variable table
drop table if exists var;
create temp table var ( value varchar(1000) );
insert into var(value) select 'WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW';
-- select
with recursive
ints(num) as
(
select 1
union all
select num+1
from ints
where num+1 <= length((select value from var))
)
,
chars(num,chr,nextChr,isGroupEnd) as
(
select tmp.*, case when tmp.nextChr <> tmp.chr then 1 else 0 end groupEnds
from (
select num,
substring((select value from var), num, 1) chr,
(select substring((select value from var), num+1, 1)) nextChr
from ints
) tmp
)
select (select value from var) plain_text, (
select string_agg(concat(cast(maxNoWithinGroup as varchar(10)) , chr), '' order by num)
from (
select *, max(noWithinGroup) over (partition by chr, groupNo) maxNoWithinGroup
from (
select num,
chr,
groupNo,
row_number() over( partition by chr, groupNo order by num) noWithinGroup
from (
select *, (select count(*)
from chars chars2
where chars2.isGroupEnd = 1 and
chars2.chr = chars.chr and
chars2.num < chars.num) groupNo
from chars
) tmp
) sub
) final
where noWithinGroup = 1
) Rle_Compressed
</syntaxhighlight>
* RLE decoding
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