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

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.

LeetCode：連結

簡單講就是，給你一個代表不同寶石的字串，和一個代表石頭的字串，從石頭字串裡找出屬於寶石的石頭，並返回個數。 
注意，區分大小寫即a和A不一樣。

class Solution(object):
    def numJewelsInStones(self, J, S):
        """
        :type J: str
        :type S: str
        :rtype: int
        """
        je_dict = {}
        for i in J:
            je_dict[i] = 1
        count = 0
        for i in S:
            if i in je_dict:
                count += 1
        return count
 

但是貌似set更快一些。

class Solution(object):
    def numJewelsInStones(self, J, S):
        """
        :type J: str
        :type S: str
        :rtype: int
        """
        jewels = set(J)
        count = 0
        for i in S:
            if i in jewels:
                count += 1
        return count