771. Jewels and Stones

leetCode

func numJewelsInStones(_ J: String, _ S: String) -> Int {
    var counter = 0
    let stones = Array(S)
    let jewels = Array(J)
    
    for i in 0..<stones.count {
        for j in 0..<jewels.count {
            let lhs = stones[i]
            let rhs = jewels[j]
            
            if lhs == rhs {
                counter += 1
            }
        }
    }
    return counter
   }