class Solution {
    func numJewelsInStones(_ J: String, _ S: String) -> Int {
        var jewelsWithCount = [Character: Int]()
        for jewel in J {
            jewelsWithCount.updateValue(0, forKey: jewel)
        }
        for stone in S {
            if let jewelCount = jewelsWithCount[stone] {
                jewelsWithCount[stone] = jewelCount + 1
            }
        }
        return jewelsWithCount.reduce(0) { $0 + $1.value }
    }
}