// practice

Practice

Problems and design prompts with explanations that connect the idea to how software runs — then try the exercise yourself.

01c plus plusIdentify C++ Memory ErrorsGiven code snippets, identify whether the error is a memory leak, dangling pointer, stack overflow, or double-free.easyReferenceSep 26, 2026
02high frequency tradingMatch Orders from a Market Data FeedGiven a sequence of market orders and an order book state, determine which orders fill at which prices.easyReferenceSep 26, 2026
03networkingCalculate Network Latency from Component DelaysGiven propagation, transmission, processing, and queuing delays, calculate the total one-way delay and round-trip time.easyReferenceSep 26, 2026
04operating systemsIdentify Process States from System CallsGiven a sequence of system calls, determine the process state transition at each step.easyReferenceSep 26, 2026
05programming algorithmsImplement Binary SearchImplement binary search that finds a target value in a sorted array in O(log n) time.easyLeetCodeSep 26, 2026
06system designDesign a Circuit BreakerImplement a circuit breaker with closed, open, and half-open states that fails fast on a degraded dependency and recovers automatically.hardreferenceSep 26, 2026
07system designDesign a Rate LimiterImplement a token bucket or fixed-window counter that allows bursts but enforces a steady request rate across many service instances.mediumleetcodeSep 26, 2026
08system designEstimate Cross-Country Request LatencyUse back-of-envelope numbers to estimate the latency of a cross-country API request and identify which hop dominates the total cost.easyreferenceSep 26, 2026
09web developmentParse an HTTP ExchangeGiven a raw HTTP request and response, identify the method, status code, headers, and body.easyReferenceSep 26, 2026
10arraysContains DuplicateDecide whether any value occurs more than once, and compare a set-based solution with sorting the input.easyLeetCodeSep 25, 2026
11arraysEncode and Decode a List of StringsDesign a reversible encoding for a list of arbitrary strings, including empty strings and embedded delimiters.mediumLeetCodeSep 25, 2026
12arraysGroup AnagramsGroup words that contain identical character counts; output group order may be arbitrary.mediumLeetCodeSep 25, 2026
13arraysLongest Consecutive SequenceReturn the length of the longest run of consecutive integer values, regardless of input order.mediumLeetCodeSep 25, 2026
14arraysMajority ElementReturn the value occurring more than half the time; the input contract guarantees one exists.easyLeetCodeSep 25, 2026
15arraysMerge Sorted ArrayMerge two sorted arrays into the first array, which has enough trailing capacity.easyLeetCodeSep 25, 2026