blob: bfdcae3f6858af515285bf6dbf557fad37843f97 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
--
-- Perl Weekly Challenge 212
-- Task 2
--
-- See <https://perlweeklychallenge.org/blog/perl-weekly-challenge-212/>
--
CREATE SCHEMA IF NOT EXISTS pwc212;
CREATE OR REPLACE FUNCTION
pwc212.task2_plpgsql( a int[], s int)
RETURNS SETOF int[]
AS $CODE$
DECLARE
current int[];
done int := 0;
next_value int;
BEGIN
-- check if the array can be divided into batches
IF mod( array_length( a, 1 ), s ) <> 0 THEN
RETURN;
END IF;
CREATE TEMPORARY TABLE IF NOT EXISTS bag( v int, c int default 1 );
TRUNCATE TABLE bag;
INSERT INTO bag
SELECT v, count(*)
FROM unnest( a ) v
GROUP BY v;
WHILE done < ( array_length( a, 1 ) / s ) LOOP
current = array[]::int[];
WHILE array_length( current, 1 ) IS NULL OR array_length( current, 1 ) < s LOOP
SELECT min( v )
INTO next_value
FROM bag
WHERE c > 0
AND v NOT IN ( SELECT * FROM unnest( current ) );
UPDATE bag
SET c = c - 1
WHERE v = next_value;
current := array_append( current, next_value );
END LOOP;
done := done + 1;
RETURN NEXT current;
END LOOP;
RETURN;
END
$CODE$
LANGUAGE plpgsql;
|
