Problem Description
You are given a 0-indexed array of string words and two integers left and right. A string is called a vowel string if it starts with a vowel character and ends with a vowel character where vowel characters are 'a', 'e', 'i', 'o', and 'u'. Return the number of vowel strings words[i] where i belongs to the inclusive range [left, right].
Key Insights
- A vowel string must start and end with a vowel.
- Vowels can be checked using a set for efficient lookup.
- The problem requires iterating over a subarray defined by the given indices.
Space and Time Complexity
Time Complexity: O(n), where n is the number of words in the specified range. Space Complexity: O(1), as we are using a constant amount of space for the vowels set.
Solution
To solve this problem, we will use a simple iteration approach. We will define a set of vowels for quick membership checking. We will then iterate through the specified range of the words array, checking if each word starts and ends with a vowel. We will maintain a count of such words and return that count at the end.