Determine if String Halves Are Alike

Determine if String Halves Are Alike

What is this problem about?

The Determine if String Halves Are Alike coding problem asks you to split an even-length string into two equal halves. You need to return true if both halves have the same number of vowels ('a', 'e', 'i', 'o', 'u', case-insensitive).

Why is this asked in interviews?

Amazon and Adobe use this "Easy" question to verify basic string manipulation and counting skills. It's a "cleanliness" test. It evaluations whether you can implement a solution without redundant code—for instance, by creating a helper function to count vowels rather than repeating the same logic for both halves.

Algorithmic pattern used

This is a simple Counting interview pattern.

1. Define a set of vowels for $O(1)$ lookup.
2. Calculate the midpoint: mid = length / 2.
3. Count vowels in the first half [0, mid).
4. Count vowels in the second half [mid, length).
5. Compare counts.

Example explanation

String: "book"

1. Halves: "bo" and "ok".
2. "bo": 1 vowel ('o').
3. "ok": 1 vowel ('o').
4. Counts match. Result: true. String: "textbook"
5. Halves: "text" and "book".
6. "text": 1 vowel ('e').
7. "book": 2 vowels ('o', 'o').
8. Result: false.

Common mistakes candidates make

• Case Sensitivity: Forgetting to handle both uppercase and lowercase vowels.
• Inefficient Sets: Checking vowels using a long if statement or a list, though for 5 vowels, the performance impact is negligible.
• Midpoint logic: Off-by-one errors when slicing the string.

Interview preparation tip

Use a String or Set containing "aeiouAEIOU" and the .indexOf() or .contains() method to check for vowels. It makes your code much cleaner than using multiple || operators.