【LeetCode】0771. Jewels and Stones

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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:

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Input: J = "aA", S = "aAAbbbb"
Output: 3

Example 2:

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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.


Related Topics:Hash Table

解題邏輯與實作

還滿簡單的一題，連想都不太需要想。題目翻譯成白話文是這樣的，給定兩個字串 J 與 S，檢查字串 S 中有多少字元屬於字串 J。不用管它寶石還石頭啦 XD


這題用暴力法逐一搜索就好了，為了改善時間複雜度，我將 J 放入 HashSet 中

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class Solution:
   def numJewelsInStones(self, J, S):
      J = set(J) 
      counter = [c for c in S if c in J]
      return len(counter)


程式碼可以進一使用 map 來化簡

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class Solution:
   def numJewelsInStones(self, J, S):
      return(sum(map(J.count,S)))

其他連結

  1. 【LeetCode】0000. 解題目錄