Verkada Inc.·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

Apr 2026Remote

Summary

Verkada coding screen, one problem the whole time. It's a Wordle-style feedback function and the duplicate letter handling is where they actually care about whether you thought it through.

Questions Asked (1)

Implement a function that takes a secret word and a guess of equal length, and returns an array where each position is marked GREEN (exact match), YELLOW (letter exists but wrong position), or GRAY (not present). Handle invalid inputs with an exception, and be careful about how duplicate letters are counted.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The basic case is fine, loop through and compare.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases, then outline a two-pass algorithm: first mark exact matches and count remaining letters, then mark yellow matches while decrementing counts. Emphasize handling duplicates correctly and validating inputs.

Pro tip: Mention that the order of marking matters: marking all exact matches first ensures that duplicate letters are not over-counted as yellow. Also, consider using a frequency map for the remaining letters to achieve O(n) time.

1. Clarify requirements and edge cases

Ask about input validation (e.g., non-string, unequal lengths), case sensitivity, and the expected exception type. Confirm the output format (e.g., array of strings or enums).

2. Design the algorithm

Plan a two-pass approach: first pass marks exact matches (GREEN) and builds a frequency map of remaining letters from the secret; second pass marks YELLOW if the letter exists in the map with count > 0, else GRAY.

3. Implement with careful duplicate handling

Code the solution, ensuring that when marking YELLOW, you decrement the count in the frequency map to avoid over-counting duplicates. Validate inputs at the start and throw an exception if invalid.

4. Test with edge cases

Test with cases like all exact matches, no matches, duplicates in secret and guess, and invalid inputs. Verify that the output matches expectations.

5. Analyze complexity and trade-offs

Discuss time and space complexity (O(n) time, O(1) space if using fixed alphabet). Mention alternative approaches (e.g., sorting) and why the two-pass method is optimal.

Key Points to Mention

Input validation: check for non-string inputs, unequal lengths, and throw an appropriate exception (e.g., IllegalArgumentException).
Two-pass algorithm: first mark exact matches, then use a frequency map for remaining letters to mark yellow.
Duplicate handling: decrement counts when marking yellow to ensure correct counts.
Time and space complexity: O(n) time, O(1) space (if alphabet size is fixed).
Edge cases: empty strings, all same letters, no matches, duplicates in both strings.
Output format: array of enums or strings representing GREEN, YELLOW, GRAY.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.