8. String to Integer (atoi)

    func myAtoi(_ str: String) -> Int {
        let arr = Array(str.trimmingCharacters(in: .whitespaces))
        var isNeg = false
        var res = 0
        for (index, char) in arr.enumerated(){
            if index == 0 && char == "-"{
                isNeg = true
            }else if index == 0 && char == "+" {
            }else if char <= "9" && char >= "0"{
                res = res * 10 + Int(String(char))!

                if !isNeg && res > Int32.max {
                    return Int(Int32.max)
                } else if isNeg && 0 - res < Int32.min {
                    return Int(Int32.min)
                }
            }else{
                break
            }
        }

        return isNeg ? 0 - res : res
    }