[스위프트3] 주민번호 체크

    static func isJumin(front: String, rear: String) -> Bool{
        if front.length < 6 {
            return false
        }
        if rear.length < 7 {
            return false
        }
        
        var chk = 0
        for i in 0..<6 {
            var str: String = substring(text: front, start: i, end: i+1)
            chk = chk + (((i % 8) + 2) * Int(str)!)
            
        }
        for i in 6..<12 {
            var str: String = substring(text: rear, start: i-6, end: i-5)
            chk = chk + (((i % 8) + 2) * Int(str)!)
        }
        
        chk = 11 - (chk % 11)
        chk = chk % 10
        if (chk != Int(substring(text: rear, start: 6, end: 7))) {
            return false
        }
        return true
    }