Given a string that consists of only uppercase English letters, you can replace any letter in the string with another letter at most k times. Find the length of a longest substring containing all repeating letters you can get after performing the above operations.
Note:
Both the string's length and k will not exceed 104.
Example 1:
Input:
s = "ABAB", k = 2
Output:
4
Explanation:
Replace the two 'A's with two 'B's or vice versa.
Example 2:
Input:
s = "AABABBA", k = 1
Output:
4
Explanation:
Replace the one 'A' in the middle with 'B' and form "AABBBBA".
The substring "BBBB" has the longest repeating letters, which is 4.
class Solution:
     def characterReplacement(self, s, k):
         """
         :type s: str
         :type k: int
         :rtype: int
         """
         start = end  = maxn = 0
         alpha_dict = collections.defaultdict(int)
         for end in range(1,len(s)+1):
             alpha_dict[s[end-1]] += 1
             maxn = max(maxn, alpha_dict[s[end-1]])
             if end-start > k+maxn:
                 alpha_dict[s[start]] -= 1
                 start += 1
         return end-start

class Solution:
     def characterReplacement(self, s, k):
         """
         :type s: str
         :type k: int
         :rtype: int
         """
         start = end  = maxn = 0
         alpha_dict = collections.defaultdict(int)
         for end in range(1,len(s)+1):
             alpha_dict[s[end-1]] += 1
             maxn = max(maxn, alpha_dict[s[end-1]])
             if end-start > k+maxn:
                 alpha_dict[s[start]] -= 1
                 start += 1
         return end-start
