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

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題目敘述

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.

解題思路

Solution

class Solution {
    public int maxVowels(String s, int k) {
        int ans = 0;

        String temp = s.substring(0, k);
        for (char t : temp.toCharArray()) {
            if (isVowel(t)){
                ans++;
            }
        }

        int cur = ans;
        for (int i = k; i < s.length(); i++) {
            if (isVowel(s.charAt(i)))
                cur++;
            if (isVowel(s.charAt(i - k)))
                cur--;
            ans = Math.max(ans, cur);
        }

        return ans;
    }

    public boolean isVowel(char c) {
        if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u')
            return true;
        return false;
    }
}