How to get missing number in Grouped data

DECLARE @tdata TABLE (grp INT, val INT)
DECLARE @dtmp TABLE (grp INT, val INT)

INSERT INTO @tdata (grp, val)
VALUES(301, 1)
INSERT INTO @tdata (grp, val)
VALUES(301, 2)
INSERT INTO @tdata (grp, val)
VALUES(301, 5)
INSERT INTO @tdata (grp, val)
VALUES(301, 7)
INSERT INTO @tdata (grp, val)
VALUES(301, 10)
INSERT INTO @tdata (grp, val)
VALUES(302, 2)
INSERT INTO @tdata (grp, val)
VALUES(303, 5)
INSERT INTO @tdata (grp, val)
VALUES(303, 6)
INSERT INTO @tdata (grp, val)
VALUES(303, 8)
INSERT INTO @tdata (grp, val)
VALUES(303, 9)

;WITH FullData AS
(
	SELECT DISTINCT t1.grp, t1.val, 1 AS nval
	FROM @tdata AS t1 LEFT JOIN (
				SELECT grp, MAX(val) AS val
				FROM @tdata
				GROUP BY grp) AS t2 ON t1.grp=t2.grp
	WHERE t1.val<=t2.val
	UNION ALL
	SELECT grp, val, nval + 1 AS nval
	FROM FullData
	WHERE nval < val
) 
INSERT INTO @dtmp (grp, val)
SELECT DISTINCT t1.grp, t1.nval as val
FROM FullData AS t1 LEFT JOIN @tdata AS t2 ON t1.grp = t2.grp 

SELECT DISTINCT grp, val
FROM @dtmp AS MissingVal
WHERE MissingVal.val NOT IN (SELECT val FROM @tdata WHERE grp = MissingVal.grp)

grp val
301 3
301 4
301 6
301 8
301 9
302 1
303 1
303 2
303 3
303 4
303 7

SELECT DISTINCT grp, val, 1 AS nval
FROM @tdata
WHERE val < 10
UNION ALL
SELECT grp, val, nval + 1 AS nval
FROM FullData
WHERE nval < 10

grp     val
301	3
301	4
301	6
301	8
301	9
302	1
302	3
302	4
302	5
302	6
302	7
302	8
302	9
302	10
303	1
303	2
303	3
303	4
303	7
303	10