func numberOfVowels(string: String) -> Int {
    var count:Int = 0

    for char in string {
        if char == "a" || char == "A" || char == "e" || char == "E" || char == "i" || char == "I" || char == "o" || char == "O" || char == "u" || char == "U" { count += 1
        }
    }
    return count
}

print (numberOfVowels(string: "Hello World!"))