Problem database last updated: June 20, 2025
10 problems · 2 Easy, 6 Medium, 2 Hard · Ranked #146 of 458
2 Easy
20% · avg 23%
6 Medium
60% · avg 59%
2 Hard
20% · avg 18%
Based on 10 reported problems, Affirm interviews are in line with industry averages - 20% Hard vs 18% overall. The majority (60%) of questions are Medium difficulty, which is typical for companies that want to see solid fundamentals without excessive trick questions.
Compared to the industry average, Affirm puts unusual emphasis on randomized (20% of problems, 21.5x the industry average), design (30% of problems, 5.2x the industry average), hash-table (60% of problems, 2.7x the industry average). If you're short on time, these are the categories to double down on.
The most common topics are hash-table (60%), string (60%), array (50%), design (30%). Problems below are sorted by frequency, the ones at the top are asked most often.
| Problem | Difficulty | Frequency | Topics | |
|---|---|---|---|---|
Insert Delete GetRandom O(1) Implement the RandomizedSet class: | Medium | Very Likely | arrayhash-tablemath | Solve |
Shortest Uncommon Substring in an Array You are given an array arr of size n consisting of non-empty strings. | Medium | Very Likely | arrayhash-tablestring | Solve |
Group Anagrams Given an array of strings strs, group the anagrams together. You can return the answer in any order. | Medium | Very Likely | arrayhash-tablestring | Solve |
Parse Lisp Expression You are given a string expression representing a Lisp-like expression to return the integer value of. | Hard | Likely | hash-tablestringstack | Solve |
Insert Delete GetRandom O(1) - Duplicates allowed RandomizedCollection is a data structure that contains a collection of numbers, possibly duplicates (i.e., a multiset). It should support inserting and removing... | Hard | Likely | arrayhash-tablemath | Solve |
String Compression Given an array of characters chars, compress it using the following algorithm: | Medium | Likely | two-pointersstring | Solve |
Valid Anagram Given two strings s and t, return true if t is an anagram of s, and false otherwise. | Easy | Likely | hash-tablestringsorting | Solve |
Coin Change You are given an integer array coins representing coins of different denominations and an integer amount representing a total amount of money. | Medium | Likely | arraydynamic-programmingbreadth-first-search | Solve |
String Compression III Given a string word, compress it using the following algorithm: | Medium | Sometimes | string | Solve |
Number of Recent Calls You have a RecentCounter class which counts the number of recent requests within a certain time frame. | Easy | Sometimes | designqueuedata-stream | Solve |
Insert Delete GetRandom O(1)
SolveImplement the RandomizedSet class:
Shortest Uncommon Substring in an Array
SolveYou are given an array arr of size n consisting of non-empty strings.
Group Anagrams
SolveGiven an array of strings strs, group the anagrams together. You can return the answer in any order.
Parse Lisp Expression
SolveYou are given a string expression representing a Lisp-like expression to return the integer value of.
Insert Delete GetRandom O(1) - Duplicates allowed
SolveRandomizedCollection is a data structure that contains a collection of numbers, possibly duplicates (i.e., a multiset). It should support inserting and removing...
String Compression
SolveGiven an array of characters chars, compress it using the following algorithm:
Valid Anagram
SolveGiven two strings s and t, return true if t is an anagram of s, and false otherwise.
Coin Change
SolveYou are given an integer array coins representing coins of different denominations and an integer amount representing a total amount of money.
String Compression III
SolveGiven a string word, compress it using the following algorithm:
Number of Recent Calls
SolveYou have a RecentCounter class which counts the number of recent requests within a certain time frame.
Frequency scores are based on crowdsourced interview reports. A higher score means the problem has been reported more often in recent Affirm interviews.
Very Likely
75-100%
Likely
50-74%
Sometimes
25-49%
Rare
0-24%
Affirm interviews focus heavily on hash-table, string, array problems. If you're short on time, these are the categories to prioritize. The problems on this page are sorted by frequency, so start from the top and work your way down.
Beyond solving problems, practice explaining your approach. Affirm interviewers care about your thought process - how you break down a problem, consider edge cases, and evaluate tradeoffs between solutions. A clean O(n) solution you can explain clearly beats an O(log n) solution you can't articulate.
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Affirm has been reported to ask 10 distinct coding problems. The most common topics are hash-table, string, array. 2 are Easy difficulty, 6 are Medium, and 2 are Hard. Problems are sorted by frequency - the ones at the top are asked most often.
Based on 10 reported problems, Affirm interviews are in line with industry averages - 20% Hard vs 18% overall. 60% of questions are Medium difficulty. Focus on the high-frequency Medium problems first, then work through the Hard ones.
Start with the highest-frequency problems listed on this page. Focus on the core topics: hash-table, string, array. Practice solving them under time pressure and explaining your approach out loud. Mock interviews with AI can simulate the real experience.
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