Problem

Solution

Intuition

This problem requires us to check whether the first and second half of a string has the same number of vowels. This is a fairly easy problem as we can simply iterate through the two halves and compare the counts of vowels in each half.

Approach

1. Initialize our vowel_counts variable to 0.
2. Iterate through the first half of the string and increment vowel_counts when we come across a vowel.
3. Iterate through the second half of the string and decrement vowel_counts when we come across a vowel.
4. Check to see if vowel_counts is 0 which would indicate they have the same number of vowels and return true if the condition is met, otherwise false.

Complexity

• Time complexity: $O(n)$. We iterate through each character of s and perform constant work per iteration.
• Space complexity: $O(1)$. We utilize a single variable which is constant in space.

Code

class Solution:
    def halvesAreAlike(self, s: str) -> bool:
        vowel_counts = 0

        for i in range(len(s) // 2):
            if s[i] in 'aeiouAEIOU':
                vowel_counts += 1
        
        for i in range(len(s) // 2, len(s)):
            if s[i] in 'aeiouAEIOU':
                vowel_counts -= 1
        
        return vowel_counts == 0