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

Description

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 <= 105
  • s consists of lowercase English letters.
  • 1 <= k <= s.length

Solutions

Solution 1

Python Code
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class Solution:
    def maxVowels(self, s: str, k: int) -> int:
        vowels = set('aeiou')
        t = sum(c in vowels for c in s[:k])
        ans = t
        for i in range(k, len(s)):
            t += s[i] in vowels
            t -= s[i - k] in vowels
            ans = max(ans, t)
        return ans

Java Code
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class Solution {
    public int maxVowels(String s, int k) {
        int t = 0, n = s.length();
        for (int i = 0; i < k; ++i) {
            if (isVowel(s.charAt(i))) {
                ++t;
            }
        }
        int ans = t;
        for (int i = k; i < n; ++i) {
            if (isVowel(s.charAt(i))) {
                ++t;
            }
            if (isVowel(s.charAt(i - k))) {
                --t;
            }
            ans = Math.max(ans, t);
        }
        return ans;
    }

    private boolean isVowel(char c) {
        return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
    }
}

C++ Code
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class Solution {
public:
    int maxVowels(string s, int k) {
        int t = 0, n = s.size();
        for (int i = 0; i < k; ++i) t += isVowel(s[i]);
        int ans = t;
        for (int i = k; i < n; ++i) {
            t += isVowel(s[i]);
            t -= isVowel(s[i - k]);
            ans = max(ans, t);
        }
        return ans;
    }

    bool isVowel(char c) {
        return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
    }
};

Go Code
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func maxVowels(s string, k int) int {
	isVowel := func(c byte) bool {
		return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u'
	}
	t := 0
	for i := 0; i < k; i++ {
		if isVowel(s[i]) {
			t++
		}
	}
	ans := t
	for i := k; i < len(s); i++ {
		if isVowel(s[i]) {
			t++
		}
		if isVowel(s[i-k]) {
			t--
		}
		ans = max(ans, t)
	}
	return ans
}

TypeScript Code
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function maxVowels(s: string, k: number): number {
    function isVowel(c) {
        return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
    }
    let t = 0;
    for (let i = 0; i < k; ++i) {
        if (isVowel(s.charAt(i))) {
            t++;
        }
    }
    let ans = t;
    for (let i = k; i < s.length; ++i) {
        if (isVowel(s.charAt(i))) {
            t++;
        }
        if (isVowel(s.charAt(i - k))) {
            t--;
        }
        ans = Math.max(ans, t);
    }
    return ans;
}

PHP Code
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class Solution {
    /**
     * @param String $s
     * @param Integer $k
     * @return Integer
     */
    function isVowel($c) {
        return $c === 'a' || $c === 'e' || $c === 'i' || $c === 'o' || $c === 'u';
    }
    function maxVowels($s, $k) {
        $cnt = 0;
        $rs = 0;
        for ($i = 0; $i < $k; $i++) {
            if ($this->isVowel($s[$i])) {
                $cnt++;
            }
        }
        $rs = $cnt;
        for ($j = $k; $j < strlen($s); $j++) {
            if ($this->isVowel($s[$j - $k])) {
                $cnt--;
            }
            if ($this->isVowel($s[$j])) {
                $cnt++;
            }
            $rs = max($rs, $cnt);
        }
        return $rs;
    }
}