Write count_common(a, b) that returns how many different values appear in both lists.
count_common([1, 2, 3], [2, 3, 4]) → 2
count_common([1, 1], [1]) → 1
Submit runs 4 tests, including hidden edge cases.
Each hint gives a little more help. Try on your own first.
Run your code to see the output here.