Find Most Frequent Vowel and Consonant

Find Most Frequent Vowel and Consonant

What is this problem about?

The Find Most Frequent Vowel and Consonant interview question is a string processing task. You are given a string and need to identify the vowel and the consonant that appear most frequently. If there are ties, you typically return the lexicographically smallest character. This Find Most Frequent Vowel and Consonant coding problem tests basic categorization and frequency tracking.

Why is this asked in interviews?

Meta and Amazon use this question to assess basic programming fluency and attention to detail. It evaluations your ability to use Hash Table interview patterns or fixed-size frequency arrays. It also checks if you can handle edge cases like strings with no vowels or no consonants.

Algorithmic pattern used

This problem follows the Frequency Counting pattern.

1. Classification: Define which characters are vowels (a, e, i, o, u). All other letters are consonants.
2. Counting: Use two hash maps or two arrays of size 26 to store counts for vowels and consonants separately.
3. Finding Max:
   • Iterate through the vowel counts to find the maximum frequency and the corresponding character (breaking ties alphabetically).
   • Do the same for consonant counts.

Example explanation

String: "leetcode"

• Vowels: e: 3, o: 1. Max frequency is 3 for 'e'.
• Consonants: l: 1, t: 1, c: 1, d: 1. Max frequency is 1. All are tied. Lexicographically smallest is 'c'. Result: e, c.

Common mistakes candidates make

• Case Sensitivity: Forgetting to convert the string to lowercase before counting.
• Tie-breaking: Returning the first character found with max frequency instead of the alphabetically smallest one.
• Non-letters: Not filtering out spaces, digits, or punctuation if the problem statement implies only letters matter.

Interview preparation tip

For small alphabets (like 'a'-'z'), a fixed-size array of length 26 is much faster and more space-efficient than a Hash Map. This is a common Array interview pattern optimization.