Data commit

Task/Run-length-encoding/SQL/run-length-encoding-2.sql

@@ -0,0 +1,62 @@
+-- variable table
+DROP TABLE IF EXISTS var;
+CREATE temp TABLE var (	VALUE VARCHAR(1000) );
+INSERT INTO var(VALUE) SELECT '1A2B3C4D5E6F';
+
+-- 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) AS
+(
+	SELECT tmp.*
+	FROM (
+	SELECT num,
+		SUBSTRING((SELECT VALUE FROM var), num, 1) chr,
+		(SELECT SUBSTRING((SELECT VALUE FROM var), num+1, 1)) nextChr
+	FROM ints
+	) tmp
+)
+,
+charsWithGroup(num,chr,nextChr,group_no) AS
+(
+	SELECT *,(SELECT COUNT(*)
+		FROM chars chars2
+		WHERE chars2.chr !~ '[0-9]' AND
+		chars2.num < chars.num) group_No
+	FROM chars
+)
+,
+charsWithGroupAndLetter(num,chr,nextChr,group_no,group_letter) AS
+(
+	SELECT *,(SELECT chr
+		FROM charsWithGroup g2
+		where g2.group_no = charsWithGroup.group_no
+		ORDER BY num DESC
+		LIMIT 1)
+	FROM charsWithGroup
+)
+,
+lettersWithCount(group_no,amount,group_letter) AS
+(
+	SELECT group_no, string_agg(chr, '' ORDER BY num), group_letter
+	FROM charsWithGroupAndLetter
+	WHERE chr ~ '[0-9]'
+	GROUP BY group_no, group_letter
+)
+,
+lettersReplicated(group_no,amount,group_letter, replicated_Letter) AS
+(
+	SELECT *, rpad(group_letter, cast(amount as int), group_letter)
+	FROM lettersWithCount
+)
+select (SELECT value FROM var) rle_encoded,
+	string_agg(replicated_Letter, '' ORDER BY group_no) decoded_string
+FROM lettersReplicated