func reverseWords(_ s: String) -> String {
        let strs = s.split(separator: " ")
        var result:String = ""
        for i in 0..<strs.count {
            if i == 0 {
               result.append("\(String(strs[i].reversed()))")
            } else {
                result.append(" \(String(strs[i].reversed()))")
            }
        }
        return result
    }