[swift] LeetCode 771. Jewels and Stones

You are 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

Note:

S and J will consist of letters and have length at most 50.

The characters in J are distinct.

return J.reduce(0) { sum, j in
            sum + S.filter({$0 == j}).count
        }

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