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--
-- Perl Weekly Challenge 256
-- Task 2
-- See <https://perlweeklychallenge.org/blog/perl-weekly-challenge-256>
--
CREATE SCHEMA IF NOT EXISTS pwc256;
CREATE OR REPLACE FUNCTION
pwc256.task2_plpgsql( lw text, rw text )
RETURNS text
AS $CODE$
DECLARE
max_index int;
output text := '';
next_char char;
BEGIN
CREATE TEMPORARY TABLE IF NOT EXISTS words( l char, r char, o int );
TRUNCATE words;
INSERT INTO words( l, o )
SELECT v, row_number() over ()
FROM regexp_split_to_table( lw, '' ) v;
INSERT INTO words( r, o )
SELECT v, row_number() over ()
FROM regexp_split_to_table( rw, '' ) v;
SELECT max( o )
INTO max_index
FROM words;
FOR i IN 1 .. max_index LOOP
SELECT l
INTO next_char
FROM words
WHERE o = i
AND l IS NOT NULL;
IF FOUND AND next_char IS NOT NULL THEN
output := output || next_char;
END IF;
SELECT r
INTO next_char
FROM words
WHERE o = i
AND r IS NOT NULL;
IF FOUND AND next_char IS NOT NULL THEN
output := output || next_char;
END IF;
END LOOP;
RETURN output;
END
$CODE$
LANGUAGE plpgsql;
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