Longest substring of all vowels in order

We can use a sliding window and a hash set to find the longest substring of all vowels in order.

class Solution:
    def longestBeautifulSubstring(self, word: str) -> int:
        if len(word) < 5:
            return 0

        l, r = 0, 0
        res = 0
        seen = set()
        while r < len(word):
            if word[r-1] > word[r]:
                l = r
                seen = set()

            seen.add(word[r])

            if len(seen) > 4:
                res = max(res, r-l+1)

            r += 1

        return res

Time complexity: O(n)
Space complexity: O(1)