LeetCode 771: Jewels and Stones

Meta Data

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Difficulty: easy First Attempt: 2022-09-06

• Submissions: Accepted → Runtime Error ×2 → Accepted

Approach

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Turn jewels into a set and check each stone in O(1) (Hash Table). Case matters.

My Attempts

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The two REs used the old parameter names J and S (NameError); renaming to jewels and stones fixed it.

Solution

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class Solution:
    def numJewelsInStones(self, jewels: str, stones: str) -> int:
        jewel_set = set(jewels)
        return sum(s in jewel_set for s in stones)

Complexity

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Time O(n + m), space O(m).

Mistakes to Avoid

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• Uppercase and lowercase are different stones.

Interview Explanation

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I put jewels in a set and count the stones that appear in it, in O(n + m).