Count vowel-only substrings with all vowels
Company: Expedia
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Technical Screen
Given a lowercase English string s, return the number of contiguous substrings that
(
1) consist only of vowels from the set {a, e, i, o, u}, and
(
2) contain each of the five vowels at least once. Constraints: 1 <= |s| <= 200000. Design an O(n) time solution using a sliding-window/two-pointer approach with O(
1) extra space. Explain how you handle consonants that break windows, repeated vowels, and long runs of vowels. Provide code and analyze time and space complexity.
Quick Answer: This question evaluates string-processing and algorithm design skills, specifically the use of sliding-window/two-pointer techniques and linear-time algorithmic optimization for counting substrings, and falls under the Coding & Algorithms domain with an emphasis on practical application rather than purely conceptual theory.