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# 1704. Determine if String Halves Are Alike

## LeetCode [1704. Determine if String Halves Are Alike](https://github.com/txfs19260817/LeetCode-Go/blob/master/solutions/title/README.md)

### Description

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.
```

**Constraints:**

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

### Tags

String

### Solution

Initialize a `count` variable to count vowels in the first half of the given string. Then traverse the last half of the string, and decrease `count` by 1 when come across a vowel. Return true if `count == 0`.

### Complexity

* Time complexity: $$O(n)$$
* Space complexity: $$O(1)$$

### Code

```go
func halvesAreAlike(s string) bool {
	var count int
	for i := 0; i < len(s)/2; i++ {
		if isVowel(s[i]) {
			count++
		}
		if isVowel(s[i+len(s)/2]) {
			count--
		}
	}
	return count == 0
}

func isVowel(c byte) bool {
	return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' || c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U'
}
```