1704. Determine if String Halves Are Alike

LeetCode 1704. Determine if String Halves Are Alike

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

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'
}