subset :: [Int] -> [Int] -> Bool
-- testing 44 combinations of argument values
-- pruning with 30/40 rules
-- looking through 0 candidates of size 1
-- looking through 2 candidates of size 2
-- looking through 3 candidates of size 3
-- looking through 9 candidates of size 4
-- looking through 22 candidates of size 5
-- looking through 47 candidates of size 6
-- looking through 132 candidates of size 7
-- looking through 323 candidates of size 8
-- looking through 854 candidates of size 9
-- looking through 2421 candidates of size 10
-- looking through 6452 candidates of size 11
-- looking through 17815 candidates of size 12
subset xs ys  =  null xs || elem (head xs) ys && subset (tail xs) ys

subset :: [Int] -> [Int] -> Bool
-- testing 44 combinations of argument values
-- pruning with 3/3 rules
-- looking through 0 candidates of size 1
-- looking through 0 candidates of size 2
-- looking through 2 candidates of size 3
-- looking through 6 candidates of size 4
-- looking through 2 candidates of size 5
subset xs ys  =  sort xs `isSubsequenceOf` sort ys