Merchant onboarding CSV validatorCodingMerchants submit their business details as rows of a simple CSV. Before a merchant can accept payments, every row must pass a set of checks. Write validaterecords(data…
Last asked Oct 2026
#parsing
- Build a transaction rule engine with an AI assistantCodingWith an AI coding assistant built into the editor, implement a rule engine that reads allow and block conditions and applies them to a list of transactions. You are graded on how…Last asked Oct 2026
+3In-memory file system with files and foldersCodingImplement an in-memory file system with path-based file and folder access, plus follow-ups on per-directory limits, duplicate names and identical contents. Covers the bank's vault…Last asked Oct 2026
+3Basic calculator IICodingEvaluate a string expression of non-negative integers with +, -, , / and spaces, no parentheses, respecting precedence (integer division truncates toward zero). Variants reported:…Last asked Sep 2026
Parse message definitions and compute their sizesCodingParse text definitions of message types made of typed fields, where a field can be another message type. Report each field's type and each message's total size from given…Last asked Sep 2026- Rebuild a task tree from parent-child records and print itCodingYou get a list of task records, each naming a task and its parent. Rebuild the hierarchy of tasks and subtasks and print it as a text tree with connector characters, in the exact…Last asked Sep 2026
- Match payments to invoices by memo and amountCodingA billing system has to match incoming payments to open invoices. Both arrive as comma-separated strings. - Invoice: invoiceid,amount,duedate. The amount is an integer in cents…Last asked Sep 2026
- Monthly AI token billing with plan switchingCodingYou are building the monthly invoice step for a chat-based AI product that charges by token usage. Each chat session produces one record, given as a comma-separated string with…Last asked Sep 2026
+2Encode and decode strings with length prefixes and count codesCodingSerialize a list of arbitrary strings into one string and back without ambiguity. A second variant decodes a compact code where some letters are written as two digits with a…Last asked Sep 2026
+1Decode stringCodingA string is encoded with the rule ktext, meaning text repeated k times; k is a positive integer that may have several digits, encoded parts can be nested, and plain letters can…Last asked Sep 2026
Reconstruct call stacks from enter and exit tracesCodingA profiler gives you call stacks sampled over time, outermost frame first. Turn them into function start and end events, then go the other way: replay start/end events into stacks…Last asked Sep 2026- Financial account ledger with acceptance, limits and settlementCodingImplement processledger(commands), which handles commands in order: set up accounts, request deposits and query balances. Return the query answers as one comma-separated string…Last asked Sep 2026
Parse a custom record format with mapped fieldsCodingParse records written in a custom text format: a few fixed comma-separated fields first (for example a machine code, a timestamp and two coded fields), then a free-form section of…Last asked Sep 2026
Parse a raw CSV string and handle corrupted rowsCodingAnother team receives data as a raw CSV payload in one string. Write code that turns it into a data structure other teams can consume. Some rows are corrupted (wrong number of…Last asked Sep 2026
Expand placeholders from a variable storeCodingImplement a small store of variables, like the export NAME="Tom" lines of a shell startup file. Any string can refer to a variable as %NAME%; expanding the string replaces each…Last asked Sep 2026
Highlight categorized phrases in a reviewCodingReviews on a travel site should show key phrases with their category. Write a function that marks every mapped phrase in a review. mapping is a list of (phrase, category) pairs…Last asked Sep 2026- Citation tagging over generated textCodingGiven generated text and source phrases, wrap every matched region in citation tags, merging overlaps and attributing each block to its sources ordered by frequency. Covers the…Last asked Sep 2026
- Reconcile bank account balances across two datasetsCoding1. From a list of balance records for bank accounts, return the latest balance of an account, in the output format the tests expect. 2. A second dataset is added. Reconcile the…Last asked Aug 2026
Parse HTML into an element tree and query itCodingYou are asked to "write an HTML parser" with no definition of the input, the output or the edge cases. Part of the exercise is pinning that down: ask for examples, then write down…Last asked Aug 2026
Parse a signed integer in any base, with overflow checksCodingWrite a production-quality parser that turns a string into a 32-bit signed integer in a given base. Handle signs, digits and letters valid for the base, and report invalid syntax…Last asked Aug 2026- Convert a hexadecimal address to dotted IPv4CodingGiven a 32-bit address written in hexadecimal, return it in dotted-decimal IPv4 form, for example C0A80001 becomes 192.168.0.1. Decide and state how you treat an optional 0x…Last asked Aug 2026
- +1Basic calculatorCodingEvaluate an arithmetic expression string with non-negative integers, +, -, , / (integer division toward zero) and spaces, respecting operator precedence, without eval. State the…Last asked Aug 2026
- Reassemble a stream of TLV messages in CCodingMessages arrive over a byte stream in type-length-value (TLV) form: a type, a length, then that many bytes of value. The stream is delivered in chunks of arbitrary size, so one…Last asked Aug 2026
- Highway toll checkpoints from plate logsCodingA highway has numbered toll checkpoints. Each checkpoint's name contains its position as a number, for example "A1" is at position 1 and "CP12" is at position 12. Ignore every…Last asked Aug 2026
- Nested list weight sum, parsed from a stringCodingA nested list holds integers and other lists. Return the sum of every integer multiplied by its depth, where the outermost list is depth 1. One version hands you the nested list…Last asked Aug 2026
- Evaluate variable definitions with forward references and cyclesCodingA list of assignments defines variables with arithmetic expressions that may use variables defined later. Evaluate them all, then report which ones are undefined because they…Last asked Aug 2026
Validate and parse a bracketed list stringCodingYou are given a string s made of lowercase letters, commas, and the parentheses ( and ). A run of letters is a word. Commas separate items. A pair of parentheses wraps a group of…Last asked Aug 2026
One-pass S-expression parser with error reportingCodingWrite a parser for a small S-expression language that reads the input character by character in a single left-to-right pass; splitting the whole string up front is not allowed. It…Last asked Aug 2026- Payment command parser and state machineCodingBuild the parser and the object-oriented state machine behind a payment command interface. Every command line has the same fixed number of positions, with empty strings in the…Last asked Aug 2026
Streaming Markdown code parserCodingParse Markdown code fences out of a token stream as it arrives, emitting complete code blocks without waiting for the whole document. Reported on 1point3acres' Cursor bank;…Last asked Jul 2026
Implement a JSON parserCodingWrite a parser that turns a JSON string into native values: objects, arrays, strings with escapes, numbers, true, false and null. Use a recursive-descent design, skip whitespace…Last asked Jun 2026- +1Evaluate nested add and sub expressionsCodingImplement evaluate(expression: str) - int, which evaluates a string written in a small function-call language. An expression is either: - an integer literal, possibly negative…Last asked Jun 2026
Evaluate a postfix expressionCodingEvaluate an arithmetic expression written in postfix (reverse Polish) notation.Last asked Jun 2026- +1Fill placeholders in a template stringCodingWrite a function that fills in a template string. template may contain placeholders written as {name}. The text between the braces is a variable name. keysi is a variable name and…Last asked May 2026
+2Exclusive time of functionsCodingFrom function start and end logs, compute each function's exclusive execution time excluding nested calls. Reported on 1point3acres' Decagon bank; reconstructed in our own words.Last asked May 2026- Account balances from a transaction logCodingA payments system receives a log of transactions and must turn it into account statements. Each log entry is a string with four comma-separated fields: - transactionid: a unique…Last asked May 2026
Resolve package versions from dependency constraintsCodingPackages have versions, and each version may require other packages within a version range. Parse the dependency specs, answer queries about which versions satisfy a constraint…Last asked May 2026- Parse and summarize HTTP access logsCodingYou get log lines, each meant to hold an IP address, a timestamp, a URL or API path and a status code. Parse each line, decide whether it is valid, and report the total number of…Last asked May 2026
- Assign code reviewers from the files changed between branchesCodingWrite a program that compares two branches of a Git repository (the reported version used the JGit library in Java), collects the files that changed, and assigns reviewers using a…Last asked Apr 2026
- Insert documents and check them against boolean predicatesCodingBuild a small server with two calls: insertdoc(filename) stores a document, and checkcontains(filename, predicate) answers whether the document satisfies a predicate over terms…Last asked Apr 2026
- Transaction fees from a CSV of paymentsCodingYou get payment transactions as a CSV string. Compute the fee for each one and the total fees per user. The rate depends on the payment type and provider and on the transaction's…Last asked Apr 2026
- Inner join of two CSV datasetsCodingTwo systems export CSV data that you need to combine. Implement: Each dataset is a list of lines. The first line is a header of comma-separated column names. Every other line is a…Last asked Apr 2026
- Valid numberCodingReturn whether a string is a valid number: an integer or decimal with an optional sign, optionally followed by an exponent (e or E and an integer). Spell out the rules first, then…Last asked Apr 2026
- Raise alerts from a streaming vmstat feedCodingRead the output of vmstat as it streams, line by line, parse the columns, and print an alert whenever a chosen metric crosses a threshold. Keep it working on a stream that never…Last asked Apr 2026
Split Markdown into chunks that keep their headersCodingSplit a Markdown file into chunks no larger than a size limit. When a new chunk starts in the middle of a section, it must begin with the headers that text sits under (for example…Last asked Apr 2026- Message latency from send and receive logsCodingTwo CSV files describe messages between two machines: one lists when machine A sent each message, the other when machine B received it. Match the rows by message and compute each…Last asked Mar 2026
Parse logs and count error codesCodingRead lines of a log, pull out the error code from each line that has one, and count how often each code appears. Skip malformed lines.Last asked Feb 2026- Decode a JWT by hand and explain browser authenticationCodingExplain how a browser stays signed in with JWTs: how the token is issued, stored and sent, and how the server checks it. Then decode a JWT string without a library: split it into…Last asked Feb 2026
- Assemble objects from chunks of an async streamCodingReads from an asynchronous stream return arbitrary chunks of bytes, so one object can be split across reads and one read can hold several objects. Write code that buffers the…Last asked Feb 2026
- Short systems utility tasks: spikes, logs and bracketsCodingSolve a few short utility problems: detect a sudden temperature spike in timestamped CPU readings, check that brackets in an expression balance, and aggregate log lines by status…Last asked Feb 2026
- Validate an IPv4 addressCodingGiven a string, decide whether it is a valid IPv4 address: four decimal numbers from 0 to 255 separated by dots, with no leading zeros and nothing else in the string.Last asked Jan 2026
- Card authorization report with fraud rulesCodingA payment platform receives authorization requests: a card holder's intent to pay a merchant. Write a function that decides each request and returns a report. Each request is a…Last asked Jan 2026
- Validate a JSON-like stringCodingWrite a validator that decides whether a string is well-formed JSON-like text: balanced braces and brackets, quoted keys, commas and colons in the right places, valid values…Last asked Jan 2026
- Build a binary tree from a parenthesized stringCodingA string encodes a binary tree as an integer followed by zero, one or two parenthesized subtrees, the left one first, for example 4(2(3)(1))(6(5)). Parse it into a tree and return…Last asked Jan 2026
- Analyse vehicle speed readings from a JSON feedCodingFetch a JSON document of nested vehicle observations and find the fastest reading and the vehicle whose speed varied the most. Follow-ups add missing readings and legitimate…Last asked Nov 2025
- Look up a value in a nested object by pathCodingGiven a nested object (maps and lists inside each other) and a path string such as a.b.0.c, return the value at that path, or a default when any step is missing. Handle list…Last asked Oct 2025
- Evaluate an arithmetic expression with variablesCodingEvaluate an arithmetic expression string with numbers, +, -, , /, parentheses and variable names whose values are given in a map. Respect precedence and parentheses, and decide…Last asked Sep 2025
- Report a user's license usage from a log fileCodingWrite a command-line script called as ./script.sh <username <logfile. Each log line looks like timestamp license user@hostname. Print the result the interviewer asks for about…Last asked Sep 2025
Write a text parser and fix the bugs in an ML projectCodingIn a one-hour round on an existing ML project: first write a parser that turns raw text data into the format the project needs, then find and fix three bugs elsewhere in a fairly…Last asked Sep 2025- +1Count the words in a documentCodingGiven the text of a document, return how many words it contains. The real work is the definition: agree with the interviewer what counts as a word (is "it's" one word or two, what…Last asked Sep 2025
- Read whole messages from a socket streamCodingWrite a reader that returns complete messages from a socket, where each read may return part of a message or several messages at once. Define the framing (for example a length…Last asked Sep 2025
- Turn dotted keys into a nested dictionaryCodingA model's weights come as a flat mapping from dotted names such as layer1.attention.query.weight to values. Convert it into a nested dictionary ({"layer1": {"attention": {"query":…Last asked Aug 2025
Parse and evaluate a Lisp-like expression with error handlingCodingEvaluate expressions such as (add 1 2), (mult 3 (add 2 3)) and (let x 2 (mult x 5)), where let binds variables in nested scopes. Unlike the classic version, the input may be…Last asked Aug 2025- Most frequent user in access logsCodingEach log entry is a string holding a username and an access timestamp. Return the user who appears most often. Discuss ties, malformed lines and logs too big for memory.Last asked Jul 2025
- Template formatter with plural blocksCodingImplement formattemplate(text: str, keys: liststr, values: liststr) - str. keysi maps to valuesi; all values are strings. text can contain two kinds of expressions in braces: 1…
- +1Remove parentheses from a plus/minus expressionCodingWrite a function simplify(expr: str) - str that removes every parenthesis from an expression and gives each term the sign it really has. Input. A valid expression made of: -…
- Shipping route cost pathsCodingA parcel carrier publishes its shipping routes as a list of strings. Each string has the form source:target:method:cost: - source and target are country codes. A route ships one…
- Regex matcher with starred groupsCodingImplement a small regex engine for a text-processing pipeline. Write ismatch(s: str, pattern: str) - bool. It returns True only when the whole string s matches pattern. The…
- Server load scores from a day of requestsCodingA load balancer team wants a daily stress report for its server fleet. You get three inputs for one day: - servers: lines serverid,basescore. Every server starts at its integer…
- Cloud usage bill from regional hourly ratesCodingYou are writing the billing step for a cloud platform. A customer's usage report says which region they ran in and how many hours they used each service. A pricing table gives the…