FreeCareerPath

Practice

Problems

Sandboxed coding rounds that run against a hidden test suite, and written questions graded against a rubric. Both, in one list.

FormatCoderpadWritten
Leveleasymediumhard
Topicimplementationsystem-designhldtreesdistributed-systemsarrays-hashingconcurrencygraphsbinary-searchconsistencydp-1dlinked-list

180 problems

Practice problems, with your status, difficulty and topics
StatusProblemFormatLevel
Not startedBest Time to Buy and Sell Stockimplementationsliding-windowCoderpadeasy
Not startedBinary Searchbinary-searchimplementationCoderpadeasy
Not startedClimbing Stairsdp-1dimplementationCoderpadeasy
Not startedContains Duplicatearrays-hashingimplementationCoderpadeasy
Not startedDiameter of Binary TreeimplementationtreesCoderpadeasy
Not startedFind a pair summing to a target, in a sorted arrayarraystwo-pointersWritteneasy
Not startedFix: Deduplicate While Preserving OrderdebuggingCoderpadeasy
Not startedFix: The Page That Skips RowsdebuggingCoderpadeasy
Not startedInvert Binary TreeimplementationtreesCoderpadeasy
Not startedKth Largest Element in a StreamheapimplementationCoderpadeasy
Not startedLast Stone WeightheapimplementationCoderpadeasy
Not startedLinked List Cycleimplementationlinked-listCoderpadeasy
Not startedMaximum Depth of Binary TreeimplementationtreesCoderpadeasy
Not startedMerge Booking WindowsimplementationCoderpadeasy
Not startedMerge Two Sorted Listsimplementationlinked-listCoderpadeasy
Not startedNumber of 1 Bitsbit-mathimplementationCoderpadeasy
Not startedReverse Linked Listimplementationlinked-listCoderpadeasy
Not startedSingle Numberbit-mathimplementationCoderpadeasy
Not startedSubtree of Another TreeimplementationtreesCoderpadeasy
Not startedTwo Sumarrays-hashingimplementationCoderpadeasy
Not startedValid Anagramarrays-hashingimplementationCoderpadeasy
Not startedValid Palindromeimplementationtwo-pointersCoderpadeasy
Not startedValid ParenthesesimplementationstackCoderpadeasy
Not started3Sumimplementationtwo-pointersCoderpadmedium
Not startedAuth Middleware BugWrittenmedium
Not startedBest Time to Buy and Sell Stock with Cooldowndp-2dimplementationCoderpadmedium
Not startedBinary Tree Level Order TraversalimplementationtreesCoderpadmedium
Not startedBinary Tree Right Side ViewimplementationtreesCoderpadmedium
Not startedBounded producer-consumer queuec++concurrencycondition-variablequeuesWrittenmedium
Not startedCheapest Flights Within K Stopsadvanced-graphsimplementationCoderpadmedium
Not startedCircuit BreakerWrittenmedium
Not startedClone GraphgraphsimplementationCoderpadmedium
Not startedCoin Changedp-1dimplementationCoderpadmedium
Not startedCombination SumbacktrackingimplementationCoderpadmedium
Not startedConnection PoolWrittenmedium
Not startedContainer With Most Waterimplementationtwo-pointersCoderpadmedium
Not startedCopy List with Random Pointerimplementationlinked-listCoderpadmedium
Not startedCORS MysteryWrittenmedium
Not startedCourse SchedulegraphsimplementationCoderpadmedium
Not startedCourse Schedule IIgraphsimplementationCoderpadmedium
Not startedDaily TemperaturesimplementationstackCoderpadmedium
Not startedDesign a notification servicehldqueuesreliabilitysystem-designWrittenmedium
Not startedDesign a rate limiterconcurrencyhldreliabilitysystem-designWrittenmedium
Not startedDesign a retry policydistributed-systemslldreliabilityWrittenmedium
Not startedDesign a text-sharing servicecachinghldstoragesystem-designWrittenmedium
Not startedDesign a URL shortenercachinghldstoragesystem-designWrittenmedium
Not startedDesign a URL shortenercachingstoragesystem-designWrittenmedium
Not startedDesign Add and Search WordsimplementationtriesCoderpadmedium
Not startedDesign an LRU cachecachingconcurrencydata-structureslldWrittenmedium
Not startedDesign notification fan-outfan-outqueuessystem-designWrittenmedium
Not startedDesign search autocompletecachingdata-structureshldsystem-designWrittenmedium
Not startedEdit Distancedp-2dimplementationCoderpadmedium
Not startedEncode and Decode Stringsarrays-hashingimplementationCoderpadmedium
Not startedEvaluate Reverse Polish NotationimplementationstackCoderpadmedium
Not startedFind Minimum in Rotated Sorted Arraybinary-searchimplementationCoderpadmedium
Not startedFind the gapsgaps-and-islandssqlwindow-functionsWrittenmedium
Not startedFix: The Invoice That Does Not BalancedebuggingCoderpadmedium
Not startedFlaky Clock TestWrittenmedium
Not startedGas StationgreedyimplementationCoderpadmedium
Not startedGraph Valid TreegraphsimplementationCoderpadmedium
Not startedGroup Anagramsarrays-hashingimplementationCoderpadmedium
Not startedHouse Robberdp-1dimplementationCoderpadmedium
Not startedHouse Robber IIdp-1dimplementationCoderpadmedium
Not startedIdempotent Payment APIWrittenmedium
Not startedImplement TrieimplementationtriesCoderpadmedium
Not startedIndex Zero Doesn't ExistWrittenmedium
Not startedInfinite RetryWrittenmedium
Not startedInsert IntervalimplementationintervalsCoderpadmedium
Not startedJump GamegreedyimplementationCoderpadmedium
Not startedJump Game IIgreedyimplementationCoderpadmedium
Not startedK Closest Points to OriginheapimplementationCoderpadmedium
Not startedKoko Eating Bananasbinary-searchimplementationCoderpadmedium
Not startedKth Largest Element in an ArrayheapimplementationCoderpadmedium
Not startedKth largest in a streamheapstreamingtop-kWrittenmedium
Not startedKth Largest in a StreamimplementationCoderpadmedium
Not startedKth Smallest Element in a BSTimplementationtreesCoderpadmedium
Not startedLast Item MissingWrittenmedium
Not startedLongest Common Subsequencedp-2dimplementationCoderpadmedium
Not startedLongest Consecutive Sequencearrays-hashingimplementationCoderpadmedium
Not startedLongest Increasing Subsequencedp-1dimplementationCoderpadmedium
Not startedLongest Palindromic Substringdp-1dimplementationCoderpadmedium
Not startedLongest Repeating Character Replacementimplementationsliding-windowCoderpadmedium
Not startedLongest run of distinct elementshash-mapsliding-windowstringsWrittenmedium
Not startedLongest Substring Without Repeating Charactersimplementationsliding-windowCoderpadmedium
Not startedLowest Common Ancestor of a BSTimplementationtreesCoderpadmedium
Not startedLRU Cacheimplementationlinked-listCoderpadmedium
Not startedLRU CacheWrittenmedium
Not startedMax Area of IslandgraphsimplementationCoderpadmedium
Not startedMaximum Product Subarraydp-1dimplementationCoderpadmedium
Not startedMaximum SubarraygreedyimplementationCoderpadmedium
Not startedMeeting Rooms IIimplementationintervalsCoderpadmedium
Not startedMerge IntervalsimplementationintervalsCoderpadmedium
Not startedMerge overlapping intervalsgreedyintervalssortingWrittenmedium
Not startedMin StackimplementationstackCoderpadmedium
Not startedMocking Too MuchWrittenmedium
Not startedMutable Default NightmareWrittenmedium
Not startedN+1 Profile PageWrittenmedium
Not startedNetwork Delay Timeadvanced-graphsimplementationCoderpadmedium
Not startedNon-overlapping IntervalsimplementationintervalsCoderpadmedium
Not startedNumber of IslandsgraphsimplementationCoderpadmedium
Not startedPacific Atlantic Water FlowgraphsimplementationCoderpadmedium
Not startedPalindrome PartitioningbacktrackingimplementationCoderpadmedium
Not startedPermutation in Stringimplementationsliding-windowCoderpadmedium
Not startedPermutationsbacktrackingimplementationCoderpadmedium
Not startedPriority Job QueueWrittenmedium
Not startedProduct of Array Except Selfarrays-hashingimplementationCoderpadmedium
Not startedRemove Nth Node From End of Listimplementationlinked-listCoderpadmedium
Not startedReorder Listimplementationlinked-listCoderpadmedium
Not startedRetry with Exponential Backoff + JitterWrittenmedium
Not startedRolling MaximumimplementationCoderpadmedium
Not startedRotting OrangesgraphsimplementationCoderpadmedium
Not startedRunning total per accountsqlwindow-functionsWrittenmedium
Not startedSearch a 2D Matrixbinary-searchimplementationCoderpadmedium
Not startedSearch a rotated sorted arrayarraysbinary-searchWrittenmedium
Not startedSearch in Rotated Sorted Arraybinary-searchimplementationCoderpadmedium
Not startedSubsetsbacktrackingimplementationCoderpadmedium
Not startedSum of Two Integersbit-mathimplementationCoderpadmedium
Not startedSuppress Duplicate AlertsimplementationCoderpadmedium
Not startedSurrounded RegionsgraphsimplementationCoderpadmedium
Not startedTake-home: a rate-limited APIapi-designrate-limitingtake-hometestingWrittenmedium
Not startedTarget Sumdp-2dimplementationCoderpadmedium
Not startedTell me about a time you broke productionbehavioralfailureownershipstarWrittenmedium
Not startedTell me about a time you disagreed with a decisionbehavioralconflictstarWrittenmedium
Not startedTell me about the most ambiguous problem you have worked onambiguitybehavioralstarWrittenmedium
Not startedThe Exception Nobody SeesWrittenmedium
Not startedThe loop that should be fast and is notc++cachememoryperformanceWrittenmedium
Not startedThe Missing CustomersWrittenmedium
Not startedThe Stale CacheWrittenmedium
Not startedThe stale closureclosuresjavascriptreactWrittenmedium
Not startedThread-Safe CounterimplementationCoderpadmedium
Not startedToken Bucket Rate LimiterWrittenmedium
Not startedTop K Frequent Elementsarrays-hashingimplementationCoderpadmedium
Not startedTwo Sum II — Sorted Inputimplementationtwo-pointersCoderpadmedium
Not startedUnique Pathsdp-2dimplementationCoderpadmedium
Not startedUsers Who Never Logged InWrittenmedium
Not startedValid Sudokuarrays-hashingimplementationCoderpadmedium
Not startedValidate Binary Search TreeimplementationtreesCoderpadmedium
Not startedVersioning an API you cannot take downapi-designrestversioningWrittenmedium
Not startedWhat does idempotent actually mean?api-designreliabilityrestWrittenmedium
Not startedWhen is an atomic not enough?atomicsc++concurrencymutexWrittenmedium
Not startedWhy did my counter get slower with more threads?c++cacheconcurrencyperformanceWrittenmedium
Not startedWord Breakdp-1dimplementationCoderpadmedium
Not startedWord SearchbacktrackingimplementationCoderpadmedium
Not startedAlien Dictionaryadvanced-graphsimplementationCoderpadhard
Not startedBinary Tree Maximum Path SumimplementationtreesCoderpadhard
Not startedDesign a chat serviceconsistencydistributed-systemshldsystem-designWrittenhard
Not startedDesign a collaborative document editorconsistencydistributed-systemshldsystem-designWrittenhard
Not startedDesign a distributed job schedulerdistributed-systemshldreliabilitysystem-designWrittenhard
Not startedDesign a distributed key-value storeconsistencydistributed-systemshldsystem-designWrittenhard
Not startedDesign a distributed rate limiterdistributed-systemsrate-limitingsystem-designWrittenhard
Not startedDesign a file sync serviceconsistencyhldstoragesystem-designWrittenhard
Not startedDesign a limit order bookdata-structureslldlow-latencytradingWrittenhard
Not startedDesign a market data distribution systemlock-freelow-latencymarket-datasystem-designWrittenhard
Not startedDesign a metrics and monitoring systemhldreliabilitystoragesystem-designWrittenhard
Not startedDesign a news feedcachingdistributed-systemshldsystem-designWrittenhard
Not startedDesign a payment system and ledgerconsistencyhldreliabilitysystem-designWrittenhard
Not startedDesign a post and follow-graph serviceconsistencydistributed-systemshldsystem-designWrittenhard
Not startedDesign a ride-matching servicedistributed-systemshldstoragesystem-designWrittenhard
Not startedDesign a ticket booking systemconcurrencyconsistencyhldsystem-designWrittenhard
Not startedDesign a video streaming servicecachinghldqueuessystem-designWrittenhard
Not startedDesign a web crawlerdistributed-systemshldstoragesystem-designWrittenhard
Not startedDesign an ad click aggregation pipelineconsistencyhldqueuessystem-designWrittenhard
Not startedDesign an object storage servicehldreliabilitystoragesystem-designWrittenhard
Not startedFewest machines to finish by a deadlinebinary-searchgreedyoptimisationWrittenhard
Not startedFind Median from Data StreamheapimplementationCoderpadhard
Not startedLargest Rectangle in HistogramimplementationstackCoderpadhard
Not startedMedian of Two Sorted Arraysbinary-searchimplementationCoderpadhard
Not startedMerge k Sorted Listsimplementationlinked-listCoderpadhard
Not startedMinimum Window Substringimplementationsliding-windowCoderpadhard
Not startedN-QueensbacktrackingimplementationCoderpadhard
Not startedSerialize and Deserialize Binary TreeimplementationtreesCoderpadhard
Not startedSliding Window Maximumimplementationsliding-windowCoderpadhard
Not startedTake-home: trade reconciliationcorrectnessdatatake-hometradingWrittenhard
Not startedThe ABA problematomicsc++concurrencylock-freeWrittenhard
Not startedTrapping Rain Waterimplementationtwo-pointersCoderpadhard
Not startedWas double-checked locking ever actually broken?c++concurrencymemory-modelsingletonWrittenhard
Not startedWhat does memory_order_relaxed actually guarantee?atomicsc++concurrencymemory-modelWrittenhard
Not startedWhat is the hardest technical problem you have solved?behavioralstartechnical-depthWrittenhard
Not startedWhy is this query slow?indexingperformancequery-planningsqlWrittenhard
Not startedWord Search IIimplementationtriesCoderpadhard