human
Solve in Python:
Given the string s, return the size of the longest substring containing each vowel an even number of times. That is, 'a', 'e', 'i', 'o', and 'u' must appear an even number of times.
 
Example 1:
Input: s = "eleetminicoworoep"
Output: 13
Explanation: The longest substring is "leetminicowor" which contains two each of the vowels: e, i and o and zero of the vowels: a and u.

Example 2:
Input: s = "leetcodeisgreat"
Output: 5
Explanation: The longest substring is "leetc" which contains two e's.

Example 3:
Input: s = "bcbcbc"
Output: 6
Explanation: In this case, the given string "bcbcbc" is the longest because all vowels: a, e, i, o and u appear zero times.

 
Constraints:

1 <= s.length <= 5 x 10^5
s contains only lowercase English letters.
 ... Can you provide a the Python code you requested?
assistant
#Here is the Python code you requested.

class Solution:
    def findTheLongestSubstring(self, s: str) -> int:
        def countVowels(ct):
            if not ct['a'] % 2 and not ct['e'] % 2 and not ct['i'] % 2 and not ct['o'] % 2 and not ct['u'] % 2:
                return True
            return False

        #Reducer
            #Slider
            #0 - len(s)
            #0 - len(s) -1 -> 1 - len(s)
        for i in range(len(s)):
            ctr = collections.Counter(s[:len(s) - i])
            for j in range(i+1):
                #window = s[j:(len(s)+j) - i]
                if j != 0:
                    ctr[s[j - 1]] -= 1
                    ctr[s[len(s)+j - i - 1]] += 1
                if countVowels(ctr):
                    return sum(ctr.values())
        return 0