1704.Determine if String Halves Are Alike
===

###### tags: `Easy`,`String`,`Counting`

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

### 題目描述

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`.

### 範例

**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.

**Constraints**:

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

### 解答

#### Javascript

function halvesAreAlike2(s) {
  const vowels = 'aeiouAEIOU';
  let count = 0;
  for (let i = 0; i < s.length / 2; i++) {
    if (vowels.includes(s[i])) count++;
    if (vowels.includes(s[s.length - 1 - i])) count--;
  }

  return count === 0;
}

> 這題用set會比較慢欸
> [name=Marsgoat] [time= Dec 1, 2022]

#### Python

class Solution:
    def halvesAreAlike(self, s: str) -> bool:
        cnt, mid = 0, len(s) // 2
        
        for idx in range(mid):
            if s[idx] in 'aeiouAEIOU': cnt += 1
            if s[mid+idx] in 'aeiouAEIOU': cnt -= 1
                    
        return cnt == 0

> [name=Kobe] [time= Dec 1, 2022]

#### Java

class Solution {
    public boolean halvesAreAlike(String s) {
        int cnt = 0;
        var vowels = Set.of('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U');
        for(int i = 0, j = s.length() - 1; i < j; i++, j--) {
            cnt += vowels.contains(s.charAt(i)) ? 1 : 0;
            cnt -= vowels.contains(s.charAt(j)) ? 1 : 0;
        }
        return cnt == 0;
    }
}

> Java 語法越來越先進
> [name=Kobe] [time= Dec 1, 2022]

#### TypeScript

- first submission

function halvesAreAlike(s: string): boolean {
  const vowels = 'aeiouAEIOU';
  const firstHalf = s.substring(0, s.length / 2);
  const lastHalf = s.substring(s.length / 2);

  let firstHalfVowelsCount: number = 0;
  let lastHalfVowelsCount: number = 0;

  firstHalf.split('').forEach((d) => {
    if (vowels.includes(d)) firstHalfVowelsCount++;
  });
  lastHalf.split('').forEach((d) => {
    if (vowels.includes(d)) lastHalfVowelsCount++;
  });

  return firstHalfVowelsCount === lastHalfVowelsCount;
}

- the 抄

function halvesAreAlike(s: string): boolean {
  const vowels = 'aeiouAEIOU';
  const firstHalf = s.substring(0, s.length / 2);
  const lastHalf = s.substring(s.length / 2);

  let count: number = 0;

  for (let i = 0; i < s.length / 2; i++) {
    if (vowels.includes(firstHalf[i])) count++;
    if (vowels.includes(lastHalf[i])) count--;
  }

  return count === 0;
}

> [name=sheep] [time= Dec 1, 2022]

### Reference

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