1 class Solution {
 2     func lengthOfLongestSubstringKDistinct(_ s:String,_ k:Int) -> Int {
 3         var res:Int = 0
 4         var left:Int = 0
 5         var m:[Character:Int] = [Character:Int]()
 6         var arrChar:[Character] = Array(s)
 7         for i in 0..<s.count
 8         {
 9             m[arrChar[i]] = i
10             while (m.count > k && left < s.count)
11             {
12                 if m[arrChar[left]] != nil && m[arrChar[left]]! == left
13                 {
14                     m[arrChar[left]] == nil
15                 }
16                 left += 1
17             }
18             res = max(res, i - left + 1)            
19         }
20         return res        
21     }
22 }
23 
24 //Character扩展 
25 extension Character  
26 {  
27   //Character转ASCII整数值(定义小写为整数值)
28    var ascii: Int {
29        get {
30            return Int(self.unicodeScalars.first?.value ?? 0)
31        }       
32     }
33 }

1 var sol = Solution()
2 print(sol.lengthOfLongestSubstringKDistinct("eceba",2))
3 //Print 3