1456. Maximum Number of Vowels in a Substring of Given Length

Medium
Given a string s and an integer k, return the maximum number of vowel letters in any substring of s with length k.
Vowel letters in English are 'a', 'e', 'i', 'o', and 'u'.
Example 1:
Input: s = "abciiidef", k = 3
Output: 3
Explanation: The substring "iii" contains 3 vowel letters.
Example 2:
Input: s = "aeiou", k = 2
Output: 2
Explanation: Any substring of length 2 contains 2 vowels.
Example 3:
Input: s = "leetcode", k = 3
Output: 2
Explanation: "lee", "eet" and "ode" contain 2 vowels.
Constraints:
  • 1 <= s.length <= 10^5
  • s consists of lowercase English letters.
  • 1 <= k <= s.length

解題

func maxVowels(s string, k int) int {
start := 0
end := 0
ans := 0
count := 0
​
for end < len(s) {
if isVowel(s[end]) { count++ }
ans = max(ans, count)
​
if end - start + 1 == k {
if isVowel(s[start]) { count-- }
start++
end++
} else {
end++
}
}
​
return ans
}
​
func isVowel(b byte) bool {
if b == 'a' || b == 'e' || b == 'i' || b == 'o' || b == 'u' {
return true
}
​
return false
}
​
func max(a, b int) int {
if a > b { return a }
return b
}