1 class Solution {
 2     func licenseKeyFormatting(_ S: String, _ K: Int) -> String {
 3         var res:[String] = [String]()
 4         for index in S.indices.reversed()
 5         {
 6             if S[index] != "-"
 7             {
 8                 if res.count % (K + 1) == K
 9                 {
10                     res.append("-")
11                 }
12                 res.append(String(S[index]))
13             }
14         }
15         //字符数组转字符串
16         var str:String = String(res.joined(separator: "").reversed())
17         return str.uppercased()
18     }
19 }

 1 class Solution {
 2     func licenseKeyFormatting(_ S: String, _ K: Int) -> String {
 3         var bufferS: String = ""
 4         var result: String = ""
 5
 6         if(S.count == 0) { return "" }
 7
 8         for c in S {
 9             if(String(c) != "-") {
10                 bufferS += (String(c)).uppercased()
11             }
12         }
13
14         var i: Int = bufferS.count % K == 0 ? K : bufferS.count % K
15         for c in bufferS {
16             if(i == 0) {
17                 result += "-"
18                 i = K
19             }
20             if(i > 0) {
21                 result += String(c)
22                 i -= 1
23             }
24         }
25
26         return result
27     }
28 }

 1 class Solution {
 2     func licenseKeyFormatting(_ S: String, _ K: Int) -> String {
 3         let s = S.replacingOccurrences(of: "-", with: "").uppercased()
 4         let chas = [Character](s)
 5
 6         var res = ""
 7         res.append(String(chas[..<(chas.count%K)]))
 8
 9         for i in stride(from: chas.count % K, to: chas.count, by: K) {
10             if !res.isEmpty {
11                 res.append("-")
12             }
13             res.append(String(chas[i..<(i+K)]))
14         }
15
16         return res
17     }
18 }

 1 class Solution {
 2     func licenseKeyFormatting(_ S: String, _ K: Int) -> String {
 3         var stringArray = S.split(separator: "-").joined(separator: "").map { String($0) }
 4
 5         var returnString: String = ""
 6
 7         while(!stringArray.isEmpty) {
 8             let subArray: String = Array(stringArray.suffix(K)).reduce("", +).uppercased()
 9             for _ in 0..<subArray.count {
10                 stringArray.removeLast()
11             }
12             returnString = stringArray.isEmpty ? "\(subArray)" + returnString : "-\(subArray)" + returnString
13
14         }
15
16         return returnString
17     }
18 }

 1 class Solution {
 2     func licenseKeyFormatting(_ S: String, _ K: Int) -> String {
 3
 4         var n = 0
 5         for c in S {
 6             if c != "-" {
 7                 n += 1
 8             }
 9         }
10
11         var num_g = n / K
12         var first = K
13         if n % K > 0 {
14             first = n % K
15             num_g += 1
16         }
17
18         var res = ""
19         var temp = ""
20         var count_g = 0
21
22         for c in S {
23             if c != "-" {
24                 temp += String(c).uppercased()
25                 if (count_g == 0 && temp.count == first && count_g != num_g-1) || (count_g < num_g-1 && temp.count == K) {
26                     res += temp + "-"
27                     temp = ""
28                     count_g += 1
29                 } else if (count_g == num_g-1 && temp.count == K) || (count_g == 0 && temp.count == first) {
30                     res += temp
31                     temp = ""
32                     count_g += 1
33                 }
34             }
35         }
36
37         return res
38     }
39 }