leetcode 771. 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 Sis 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.

class Solution(object):
    def numJewelsInStones(self, J, S):
        """
        :type J: str
        :type S: str
        :rtype: int
        out("", "")=0
        out("", "A")=0
        out("A", "")=0
        out("AB", "C")=0
        out("C", "AB")=0
        out("AB", "AB")=0
        out("ABC", "DEF")=0
        out("ABC", "ABc")=2
        out("ABC", "ABCD")=3
        """
        
        
        '''
        if not J:
            return 0
        jewels = set()
        for j in J:
            jewels.add(j)
        ans = 0
        for s in S:
            if s in jewels:
                ans += 1
        return ans
        '''
    
        setJ = set(J)
        return sum(s in setJ for s in S)
        

时间复杂度O(S+J) 空间复杂度 O(S+J)

注： sum([True, False, True])==2