How do you check if two strings are anagrams? | Interview Question

Q: How do you check if two strings are anagrams?

**Target Audience:** Beginners preparing for coding interviews — you know Python strings, loops and dicts; nothing else assumed. **Difficulty:** Easy **Language:** Python 3 > **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Every output shown was produced by running the code with `python3` (3.13); nothing is typed in by hand. ## 1. Why This Even Matters — A Story First Two friends are playing a word game. Each has a little bag of letter tiles, and you want to know: **do the two bags hold exactly the same tiles?** Not the same word — the same tiles. "listen" and "silent" would pass; "rat" and "car" would not; "aab" and "abb" would not either, even though both use only `a` and `b`. There are two natural ways to check. 1. **Line them up.** Pour each bag out and arrange the tiles alphabetically. "listen" becomes `e i l n s t`, and so does "silent". If the two rows

The problem

Question presented to candidate: "Write a Python function that takes two strings and returns whether one is an anagram of the other — same characters, same number of times, any order. Then tell me its complexity and how you would change it if case and spaces should be ignored."

What a strong answer should cover:

The definition in terms of counts: anagrams have identical character frequencies, and different lengths mean False immediately.
Two solutions: sorted(s) == sorted(t) in O(n log n), and counting in O(n) with a dict or collections.Counter.
Space: O(k) for the counts (k distinct characters), or O(1) with a 26-slot list when input is guaranteed a–z.
Normalising both strings the same way (.lower(), removing spaces) when the rules say case and spaces do not count.
Python specifics: Counter(s) == Counter(t) is the idiomatic one-liner; sorted() on a str returns a list; Python strings are sequences of code points, but visually identical text can still differ (composed vs decomposed accents) without unicodedata.normalize.

Clarifying questions expected:

Case-sensitive? Do spaces and punctuation count?
Only lowercase a–z, or any Unicode?

Code / implementation expected: Yes — an is_anagram(s, t) function in Python, ideally the O(n) counting version, run on a few true/false cases.

strings
hashing

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Solution

Target Audience: Beginners preparing for coding interviews — you know Python strings, loops and dicts; nothing else assumed. Difficulty: Easy Language: Python 3

How to read this doc: Every idea is explained in plain language first, then tagged with 📌 Interview term: so you also learn the exact words an interviewer expects. Every output shown was produced by running the code with python3 (3.13); nothing is typed in by hand.

1. Why This Even Matters — A Story First

Two friends are playing a word game. Each has a little bag of letter tiles, and you want to know: do the two bags hold exactly the same tiles? Not the same word — the same tiles. "listen" and "silent" would pass; "rat" and "car" would not; "aab" and "abb" would not either, even though both use only a and b.

There are two natural ways to check.

Line them up. Pour each bag out and arra

The solution is hidden so you can try first

14 min read · 11 sections

Python code

Edit the code and run it here. Each printed line with an expected value becomes a test.

PythonCounting anagram check on eight inputs, including case and spaces

Practice

PythonSorting vs hash-map counting vs 26-slot array: all three agree

Practice

Discussion

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