let numbers = ["500", "50", "1000"]

for num in numbers {
    switch num.count {
    case 0:
        print("0.00")
    case 1:
        print("0.0" + num)
    case 2:
        print("0." + num)
    default:
        var result = num
        let dotIndex = num.index(num.endIndex, offsetBy: -2)
        result.insert(".", at: dotIndex)
        print(result)
    }
}