[Swift]LeetCode340.最多有K個不一樣字符的最長子串 $ Longest Substring with At Most K Distinct Characters

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Given a string, find the length of the longest substring T that contains at most k distinct characters.

For example, Given s = "eceba" and k = 2,

T is "ece" which its length is 3.

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給定一個字符串，找出包含最多k個不一樣字符的最長子字符串t的長度。

例如，給定s=「eceba」和k=2，

T是「ece」，其長度爲3。

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Solution:

 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擴展 
25 extension Character  
26 {  
27   //Character轉ASCII整數值(定義小寫爲整數值)
28    var ascii: Int {
29        get {
30            return Int(self.unicodeScalars.first?.value ?? 0)
31        }       
32     }
33 }

---

點擊：Playground測試

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