170. Vowel-Rich Window
A lighthouse keeper logs the day's radio chatter as a lowercase string s. To find the clearest stretch of speech, she measures the vowel richness of a stretch: how many of its characters are one of a, e, i, o or u.
Given s and an integer k, look at every substring made of exactly k consecutive characters and return the largest vowel richness among them. A stretch may contain no vowels at all, in which case its richness is 0.
Example 1
- Input:
- s = "quietsea", k = 3
- Output:
- 3
- Explanation:
The windows are qui (2), uie (3), iet (2), ets (1), tse (1) and sea (2). The best is uie with 3 vowels.
Example 2
- Input:
- s = "rhythm", k = 2
- Output:
- 0
- Explanation:
No window contains a vowel, so the answer is 0.
Constraints
1 ≤ k ≤ s.length ≤ 105
s consists of lowercase English letters.
How this problem is judged
- Answers
- Your answer must match exactly. Numbers compare by value, so 2 and 2.0 are equal.
Expected complexity
- Time
- O(n)
- Space
- O(1)