You're given strings J representing the types of stones that are jewels, and
S representing the stones you have. Each character in S is a
type of stone you have. You want to know how many of the stones you have are also
jewels.
The letters in J are guaranteed distinct, and all characters in J
and S are letters. Letters are case sensitive, so "a" is
considered a different type of stone from "A".
Example 1:
Input: J = "aA", S = "aAAbbbb" Output: 3
Example 2:
Input: J = "z", S = "ZZ" Output: 0
Note:
S and J will consist of letters and have length at most 50.
J are distinct.