Tokenizer Implementation

Phone ScreenAnthropicLast reported July 2026High Frequency

Reported: 14× across candidate reports
First seen: February 2025
Last reported: July 2026
Also asked in: Behavioral, Coding
Reported outcome: mixed

Problem Overview

You are given a vocabulary dictionary mapping strings (tokens) to integer IDs, e.g. {'a': 1, 'b': 2, 'cd': 3, 'UNK': -1}, and an input text string. Part 1 – Code Reading / Bug Finding: A baseline tokenize(text, vocab) is provided. It builds a running key character by character; whenever the…

4 candidate-reported follow-ups — the exact probes interviewers asked, with the trigger for each
The rest of the problem statement — full requirements, constraints, and edge cases
Approach and trade-offs — what passing candidates did, and the mistakes that sink people

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Interviewer Follow-ups

The exact follow-ups reported by candidates, with the trigger that prompts each one — plus the mistakes that sink people.