# 771. Jewels and Stones

**<font color=red>难度: Easy</font>**

## 刷题内容

> 原题连接

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

> 内容描述

```
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.
```

## 解题方案

> 思路 1
******- 时间复杂度: O(J+S)******- 空间复杂度: O(S)******

beats 18.06%

```python
class Solution(object):
    def numJewelsInStones(self, J, S):
        """
        :type J: str
        :type S: str
        :rtype: int
        """
        J = set(J)
        res = 0
        cnt = collections.Counter(S)
        for s, times in cnt.items():
            if s in J:
                res += times
        return res
```




























