8.19 - hard - 71

340. Longest Substring with At Most K Distinct Characters

这题是典型的前向型指针的模板题

class Solution(object):
   def lengthOfLongestSubstringKDistinct(self, s, k):
       """
       :type s: str
       :type k: int
       :rtype: int
       """
       if k == 0:
           return 0
       hash = {}
       j = 0
       counter = 0
       res = 0
       for i in range(len(s)):
           while j < len(s) and (s[j] in hash or counter < k):
               if s[j] in hash:
                   hash[s[j]] += 1
               else:
                   hash[s[j]] = 1
                   counter += 1
               res = max(res, j-i+1)
               j += 1
           hash[s[i]] -= 1
           if hash[s[i]] == 0:
               hash.pop(s[i], 0)
               counter -= 1
       
       return res