[Swift]LeetCode340.最多有K个不同字符的最长子串 $ 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.

---

给定一个字符串，找出包含最多k个不同字符的最长子字符串t的长度。

例如，给定s=“eceba”和k=2，

T是“ece”，其长度为3。

---

Solution:

class Solution {
    func lengthOfLongestSubstringKDistinct(_ s:String,_ k:Int) -> Int {
        var res:Int = 0
        var left:Int = 0
        var m:[Character:Int] = [Character:Int]()
        var arrChar:[Character] = Array(s)
        for i in 0..<s.count
        {
            m[arrChar[i]] = i
            while (m.count > k && left < s.count)
            {
                if m[arrChar[left]] != nil && m[arrChar[left]]! == left
                {
                    m[arrChar[left]] == nil
                }
                left += 1
            }
            res = max(res, i - left + 1)            
        }
        return res        
    }
}

//Character扩展 
extension Character  
{  
  //Character转ASCII整数值(定义小写为整数值)
   var ascii: Int {
       get {
           return Int(self.unicodeScalars.first?.value ?? 0)
       }       
    }
}

---

点击：Playground测试

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