Find the Longest Even-Length Word
Company: Walmart Labs
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: easy
Interview Round: Technical Screen
# Find the Longest Even-Length Word
Implement `longest_even_word(sentence)`. Words are separated by one or more spaces. Return the first word among those having the greatest positive even length. Return `"00"` when `sentence` is empty, contains only spaces, or contains no even-length word. The input is always a non-null string in every language.
Examples:
- `"Time to write great code"` returns `"Time"`.
- `"a cat sun"` returns `"00"`.
Constraints: at most `200000` characters; words contain English letters. Process the sentence in one pass over its words.
```hint Preserve first-on-tie behavior
Update the answer only when a strictly longer eligible word appears.
```
Quick Answer: Implement `longest_even_word(sentence)`. Work through the function contract, boundary cases, correctness argument, and time and space complexity expected in a production-quality solution.
Words in a non-null sentence are separated by one or more spaces. Return the first word among those with the greatest positive even length. Return `00` when the sentence is empty, contains only spaces, or contains no even-length word. Words contain only English letters.
Constraints
- 0 <= len(sentence) <= 200000; sentence is non-null.
- Words contain English letters and are separated by one or more spaces.
- Only positive even word lengths qualify; equal maximum lengths return the first word, and no qualifying word returns 00.
Examples
Input: ('',)
Expected Output: '00'
Explanation: An empty sentence returns the sentinel.
Input: (' ',)
Expected Output: '00'
Explanation: A sentence containing only spaces returns the sentinel.
Hints
- Test empty and spaces-only sentences, one word, and a sentence with no even-length word.
- Include several equal-length eligible words and verify the first one is returned.
- Use leading, trailing, and repeated spaces together with a later strictly longer eligible word.