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 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


  • S and J will consist of letters and have length at most 50.
  • The characters in J are distinct.


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)

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