Formatted question description: https://leetcode.ca/all/1704.html

1704. Determine if String Halves Are Alike (Easy)

You are given a string s of even length. Split this string into two halves of equal lengths, and let a be the first half and b be the second half.

Two strings are alike if they have the same number of vowels ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'). Notice that s contains uppercase and lowercase letters.

Return true if a and b are alike. Otherwise, return false.

Example 1:

Input: s = "book"
Output: true
Explanation: a = "bo" and b = "ok". a has 1 vowel and b has 1 vowel. Therefore, they are alike.

Example 2:

Input: s = "textbook"
Output: false
Explanation: a = "text" and b = "book". a has 1 vowel whereas b has 2. Therefore, they are not alike.
Notice that the vowel o is counted twice.

Example 3:

Input: s = "MerryChristmas"
Output: false

Example 4:

Input: s = "AbCdEfGh"
Output: true

Constraints:

2 <= s.length <= 1000
s.length is even.
s consists of uppercase and lowercase letters.

Related Topics:
String

Solution 1.

class Solution {
    public boolean halvesAreAlike(String s) {
        s = s.toLowerCase();
        int length = s.length();
        int halfLength = length / 2;
        int vowels1 = 0, vowels2 = 0;
        for (int i = 0; i < halfLength; i++) {
            char c1 = s.charAt(i), c2 = s.charAt(i + halfLength);
            if (isVowel(c1))
                vowels1++;
            if (isVowel(c2))
                vowels2++;
        }
        return vowels1 == vowels2;
    }

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

############

class Solution {
    private static final Set<Character> VOWELS
        = Set.of('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U');

    public boolean halvesAreAlike(String s) {
        int cnt = 0, n = s.length() >> 1;
        for (int i = 0; i < n; ++i) {
            cnt += VOWELS.contains(s.charAt(i)) ? 1 : 0;
            cnt -= VOWELS.contains(s.charAt(i + n)) ? 1 : 0;
        }
        return cnt == 0;
    }
}

// OJ: https://leetcode.com/problems/determine-if-string-halves-are-alike/
// Time: O(N)
// Space: O(N)
class Solution {
    int count(string s) {
        int cnt = 0;
        for (char c : s) {
            c = tolower(c);
            cnt += c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
        }
        return cnt;
    }
public:
    bool halvesAreAlike(string s) {
        return count(s.substr(0, s.size() / 2)) == count(s.substr(s.size() / 2));
    }
};

class Solution:
    def halvesAreAlike(self, s: str) -> bool:
        cnt, n = 0, len(s) >> 1
        vowels = set('aeiouAEIOU')
        for i in range(n):
            cnt += s[i] in vowels
            cnt -= s[i + n] in vowels
        return cnt == 0

############

# 1704. Determine if String Halves Are Alike
# https://leetcode.com/problems/determine-if-string-halves-are-alike/

class Solution:
    def halvesAreAlike(self, s: str) -> bool:
        half = len(s) // 2

        def count(s):
            return sum(c in "aeiouAEIOU" for c in s)
        
        return count(s[:half]) == count(s[half:])
        
        

func halvesAreAlike(s string) bool {
	vowels := map[byte]bool{}
	for _, c := range "aeiouAEIOU" {
		vowels[byte(c)] = true
	}
	cnt, n := 0, len(s)>>1
	for i := 0; i < n; i++ {
		if vowels[s[i]] {
			cnt++
		}
		if vowels[s[i+n]] {
			cnt--
		}
	}
	return cnt == 0
}

function halvesAreAlike(s: string): boolean {
    const set = new Set(['a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U']);
    const n = s.length >> 1;
    let count = 0;
    for (let i = 0; i < n; i++) {
        set.has(s[i]) && count++;
        set.has(s[n + i]) && count--;
    }
    return count === 0;
}

use std::collections::HashSet;
impl Solution {
    pub fn halves_are_alike(s: String) -> bool {
        let set: HashSet<&u8> = [b'a', b'e', b'i', b'o', b'u', b'A', b'E', b'I', b'O', b'U']
            .into_iter()
            .collect();
        let s = s.as_bytes();
        let n = s.len() >> 1;
        let mut count = 0;
        for i in 0..n {
            if set.contains(&s[i]) {
                count += 1;
            }
            if set.contains(&s[n + i]) {
                count -= 1;
            }
        }
        count == 0
    }
}

/**
 * @param {string} s
 * @return {boolean}
 */
var halvesAreAlike = function (s) {
    const str = 'aeiouAEIOU';
    let cnt = 0;
    for (let i = 0; i < s.length / 2; i++) {
        if (str.indexOf(s[i]) > -1) cnt++;
        if (str.indexOf(s[s.length - 1 - i]) > -1) cnt--;
    }
    return cnt === 0;
};

class Solution {
    /**
     * @param String $s
     * @return Boolean
     */
    function halvesAreAlike($s) {
        $cnt = 0;
        for ($i = 0; $i < strlen($s) / 2; $i++) {
            if (strpos("aeiouAEIOU", $s[$i]) !== false) $cnt++;
            if (strpos("aeiouAEIOU", $s[strlen($s) / 2 + $i]) !== false) $cnt--;
        }
        return $cnt == 0;
    }
}

1704 - Determine if String Halves Are Alike

1704. Determine if String Halves Are Alike (Easy)

Solution 1.

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1704. Determine if String Halves Are Alike (Easy)

Solution 1.

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