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771. Jewels and Stones 👍

  • Time: $O(|\texttt{jewels}| + |\texttt{stones}|)$
  • Space: $O(|\texttt{jewels}|)$
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class Solution {
 public:
  int numJewelsInStones(string jewels, string stones) {
    int ans = 0;
    unordered_set<char> jewelsSet(jewels.begin(), jewels.end());

    for (const char stone : stones)
      if (jewelsSet.contains(stone))
        ++ans;

    return ans;
  }
};

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class Solution {
  public int numJewelsInStones(String jewels, String stones) {
    int ans = 0;
    Set<Character> jewelsSet = jewels.chars().mapToObj(c -> (char) c).collect(Collectors.toSet());

    for (final char stone : stones.toCharArray())
      if (jewelsSet.contains(stone))
        ++ans;

    return ans;
  }
}

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