Easy

Meta-styleAmazon-style

Group Words by Letter Composition DSA Interview

Given a list of lowercase words, group together the words that share the exact same multiset of letters.

1. Problem Statement

You are given a list of lowercase words. Group together words that are rearrangements of each other's letters, and return the groups.

2. Live Coding Format

Choose Python, JavaScript, Java, or C++, then solve while explaining your reasoning to the live interviewer.

Validation uses handwritten tests only. The MVP does not compile or run code, and it does not provide AI algorithm completion.

3. Key Focus Areas

1
Problem clarification and contract
2
Approach exploration and optimality
3
Think-aloud communication and pacing
4
Implementation correctness
5
Code quality and language fluency
6
Handwritten tests and dry run
7
Debugging and self-correction
8
Complexity analysis
9
Follow-up performance

4. What Strong Candidates Should Demonstrate

✓Clarify grouping semantics, ordering guarantees, and character-set assumptions before coding.
✓Explain a naive pairwise-comparison baseline and improve to a canonical-key hash map grouping.
✓Think aloud while implementing readable, correct grouping logic.
✓Validate with explicit expected outputs and a top-to-bottom handwritten dry run.
✓Analyze time and space complexity and pace the easy core problem to leave room for a coding follow-up.

Evaluation Guide

This is an evaluation framework, not a single model answer. Strong designs may make different choices when their assumptions and trade-offs are explicit.

Problem clarification and contract

10%

Senior signals

✓Clarifies whether output group order or in-group word order matters, whether words repeat, and whether input is guaranteed lowercase ASCII.
✓Confirms how single-word groups and an empty input list should be handled.

Staff-level signals

◆Raises whether the function must be stable/deterministic across repeated calls for a production caller.

Common red flags

×Starts coding without confirming what defines two words as being in the same group.

Approach exploration and optimality

20%

Senior signals

✓Explains an all-pairs comparison baseline, identifies its repeated-work bottleneck, and improves to a canonical-key hash map grouping (sorted string or 26-length letter count signature).
✓Compares the sorted-key approach against a counting-signature key and picks one with a stated rationale.

Staff-level signals

◆Discusses behavior for very long words or a very large word list where key construction cost matters.

Common red flags

×Starts implementation without explaining an approach even after one interviewer prompt.

Think-aloud communication and pacing

10%

Senior signals

✓Explains the plan before coding and narrates the canonical-key idea while implementing.
✓Completes the easy core problem efficiently enough to leave meaningful time for a follow-up.

Common red flags

×Writes substantial code silently and cannot explain what the code is doing.
×Spends most of the interview on the easy core problem and leaves insufficient time for a follow-up.

Implementation correctness

25%

Senior signals

✓Implements a correct grouping using a canonical key mapped to a list of original words.
✓Handles duplicate words, single-letter words, and an empty input list.
✓Provides a convincing argument for why the chosen key is a valid canonical form.

Common red flags

×Groups words incorrectly (e.g., by length instead of letter composition) or drops words from the output.
×Final code contains a material correctness bug that the candidate does not identify.

Code quality and language fluency

15%

Senior signals

✓Produces readable, language-appropriate code with clear names and a defined structure for the returned groups.

Staff-level signals

◆Mentions Unicode or locale-sensitive sorting only when it is relevant.

Common red flags

×Contains key/value confusion or syntax-level incoherence that prevents credible reasoning.

Handwritten validation, dry run, and debugging

10%

Senior signals

✓Provides explicit inputs and expected outputs before tracing the code from top to bottom.
✓Covers duplicates, single-word groups, and an empty list.
✓Finds and fixes an error independently, then re-validates the affected path.

Common red flags

×Claims the code works without a representative trace.

Complexity analysis and follow-up

10%

Senior signals

✓States time complexity in terms of total characters and number of words, and auxiliary space for the hash map.

Staff-level signals

◆Compares sorted-key cost versus counting-signature cost with a stated tradeoff.

Common red flags

×Cannot state the complexity of the implemented solution.
×Fails a reasonable follow-up after solving an easy first problem, despite having at least five minutes and receiving bounded clarification.

Trade-offs to articulate

All-pairs comparison avoids extra key construction but costs quadratic time in the number of words.
A sorted-string key is simple but costs O(k log k) per word for word length k.
A 26-count signature key avoids sorting but costs a fixed 26-slot pass per word.

Practice follow-up questions

1.Coding follow-up: given the grouped output, return only the groups with more than one member, sorted by descending group size with ties broken by first-appearance order.
2.Verbal extension: how would the approach change if words could contain uppercase letters or accented characters?

Want interactive feedback?

Practice this problem in the live coding workspace while the interviewer probes your clarification, algorithm, implementation, complexity, and handwritten tests.

Start Interview

Core Concepts

ArraysHash MapsString CanonicalizationComplexity Analysis