771. Jewels and Stones

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Jewels and Stones

题目描述

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.

题目大意

求 S 中有多少个 J 中的字母，区分大小写。

解题思路

辅助字典，暴力搜索

代码

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class Solution {
    func numJewelsInStones(_ J: String, _ S: String) -> Int {
        var dict = [Character: Int]()
        for char in J {
            dict[char] = 1
        }
        var ans = 0
        for char in S {
            if dict[char] != nil {
                ans += 1
            }
        }
        return ans
    }
}
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