## Description

https://leetcode.com/problems/jewels-and-stones/

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.- The characters in
`J`

are distinct.

## Explanation

Simply count how many stones in jewels.

## Python Solution

```
class Solution:
def numJewelsInStones(self, J: str, S: str) -> int:
J = set(J)
count = 0
for c in S:
if c in J:
count += 1
return count
```

- Time Complexity: O(J.length + S.length)
- Space Complexity: O(J.length)