var str = "10239485728"

var bankList = ["Bank 1", "Bank 2", "Bank 3"]

func getBanks(_ allbanks: [String],_  accountNo: String) -> [String]{
    var result = ["1","2","3","4"]
    let start = String.Index(encodedOffset: 0)
    let end = String.Index(encodedOffset: accountNo.count - 1)
    let sumsample = String(accountNo[start..<end])
    var sumcount = 0
    var sum = 0

    for ch in Array(sumsample)  {
        var s = [String]()
        s.append(String(ch))
        switch sumcount {
        case 0:
            if let number = Int(String(ch)) {
                sum += number * 3
            }
        case 1:
            if let number = Int(String(ch)) {
                sum += number * 7
            }
        case 2:
            if let number = Int(String(ch)) {
                sum += number * 3
            }
        default:
            print("Nothing")
        }
        print("Hello, \(ch)!")
    }

    for fullBankList in allbanks{
        if(fullBankList == "0"){
            var a = Int(fullBankList)! + sum
            var b = a % 10
            var check = b == 0 ? 0 : 10 - b
            if(check == Int(accountNo)){
                result.append(fullBankList)

            }
        }
    }
    return result
}
print(getBanks(bankList, str))