Return the maximum number of vowel letters in any substring of s with length k.

Vowel letters in English are (a, e, i, o, 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.

Example 4:

Input: s = "rhythms", k = 4
Output: 0
Explanation: We can see that s doesn't have any vowel letters.

Example 5:

Input: s = "tryhard", k = 4
Output: 1

Constraints:

• 1 <= s.length <= 10^5
• s consists of lowercase English letters.
• 1 <= k <= s.length

Solution: Sliding Window

Keep tracking the number of vows in a window of size k.

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

// Author: Huahua
class Solution {
public:
  int maxVowels(string s, int k) {    
    vector<int> v(128);
    v['a'] = v['e'] = v['i'] = v['o'] = v['u'] = 1;
    int total = 0;
    int ans = 0;
    for (int i = 1; i <= s.length(); ++i) {
      total += v[s[i - 1]];
      if (i >= k) {
        ans = max(ans, total);
        total -= v[s[i - k]];
      }
    }
    return ans;
  }
};

The post 花花酱 LeetCode 1456. Maximum Number of Vowels in a Substring of Given Length appeared first on Huahua's Tech Road.