Jewels and Stones

You're given strings jewels representing the types of stones that are jewels, and stones representing the stones you have. Each character in stones is a type of stone you have. You want to know how many of the stones you have are also jewels.

Letters are case sensitive, so "a" is considered a different type of stone from "A".

Example 1:

Input: jewels = "aA", stones = "aAAbbbb"
Output: 3

Example 2:

Input: jewels = "z", stones = "ZZ"
Output: 0

Solution

class Solution:
    def numJewelsInStones(self, jewels: str, stones: str) -> int:
        cnt = 0
        for j in jewels:
            cnt += stones.count(j)
        return cnt