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

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

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, 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

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Solution

• mine

  • Java

    Runtime: 7 ms, faster than 99.18%, Memory Usage: 40.2 MB, less than 100.00% of Java online submissions

    //O(N)time O(1)space
    public int maxVowels(String s, int k) {
        int[] map = new int[26];
        map['a' - 'a'] = 1;
        map['e' - 'a'] = 1;
        map['i' - 'a'] = 1;
        map['o' - 'a'] = 1;
        map['u' - 'a'] = 1;
    
        int res = 0;
        int len = s.length();
        int temp = 0;
        for (int i = 0; i < len; i++) {
            if (i - k >= 0 && map[s.charAt(i - k) - 'a'] == 1){
                temp--;
            }
            if (map[s.charAt(i) - 'a'] == 1){
                temp++;
            }
            res = Math.max(res,temp);
        }
        return res;
    }