Citadel
Rigorous quantitative loops — algorithms with tight complexity expectations, probability, and questions about how your systems behave under latency and load.
Typical loop
- 1Recruiter screen
- 2Online assessment: timed coding
- 3Technical phone screen
- 4Onsite: algorithms, probability, and systems rounds
- 5Final round with the desk or team
Questions
Callback's practice questions and the LeetCode questions Citadel has been asking, filtered together.
Asked on LeetCode
87 questions · all time
- Sliding Window MaximumhardArrayQueueSliding WindowHeap (Priority Queue)+2frequency 100.0
- Count Palindromic SubsequenceshardStringDynamic Programmingfrequency 98.6
- Palindromic SubstringsmediumTwo PointersStringDynamic Programmingfrequency 93.8
- Best Time to Buy and Sell StockeasyArrayDynamic Programmingfrequency 89.9
- Best Position for a Service CentrehardArrayMathGeometryRandomizedfrequency 87.8
- Find Median from Data StreamhardTwo PointersDesignSortingHeap (Priority Queue)+1frequency 87.8
- Merge IntervalsmediumArraySortingQuicksortfrequency 87.8
- Number of Orders in the BacklogmediumArrayHeap (Priority Queue)Simulationfrequency 85.4
- LRU CachemediumHash TableLinked ListDesignDoubly-Linked Listfrequency 82.8
- Maximum Total Damage With Spell CastingmediumArrayHash TableTwo PointersBinary Search+3frequency 82.8
- Minimum Costs Using the Train LinehardArrayDynamic Programmingfrequency 82.8
- Minimum Operations to Make Numbers Non-positivehardArrayBinary Searchfrequency 82.8
- Evaluate DivisionmediumArrayStringDepth-First SearchBreadth-First Search+5frequency 79.9
- First Completely Painted Row or ColumnmediumArrayHash TableMatrixfrequency 79.9
- Maximum Length of Repeated SubarraymediumArrayBinary SearchDynamic ProgrammingSliding Window+2frequency 79.9
- Insert Delete GetRandom O(1)mediumArrayHash TableMathDesign+1frequency 76.5
- Parallel Courses IIIhardArrayDynamic ProgrammingGraph TheoryTopological Sort+1frequency 76.5
- Employee Free TimehardArraySweep LineSortingHeap (Priority Queue)frequency 72.7
- Find the Duplicate NumbermediumArrayTwo PointersBinary SearchBit Manipulation+2frequency 72.7
- LFU CachehardHash TableLinked ListDesignDoubly-Linked Listfrequency 72.7
- Meeting SchedulermediumArrayTwo PointersSortingfrequency 72.7
- Time Based Key-Value StoremediumHash TableStringBinary SearchDesignfrequency 72.7
- Design Circular QueuemediumArrayLinked ListDesignQueuefrequency 68.2
- Find Servers That Handled Most Number of RequestshardArrayHeap (Priority Queue)SimulationOrdered Setfrequency 68.2
- Fizz BuzzeasyMathStringSimulationfrequency 68.2
- Serialize and Deserialize Binary TreehardStringTreeDepth-First SearchBreadth-First Search+2frequency 68.2
- Smallest Missing Non-negative Integer After OperationsmediumArrayHash TableMathGreedyfrequency 68.2
- Sqrt(x)easyMathBinary SearchNewton's Methodfrequency 68.2
- Binary Tree Maximum Path SumhardDynamic ProgrammingTreeDepth-First SearchBinary Tree+1frequency 62.7
- Couples Holding HandshardGreedyDepth-First SearchBreadth-First SearchUnion-Find+1frequency 62.7
- Course Schedule IImediumDepth-First SearchBreadth-First SearchGraph TheoryTopological Sortfrequency 62.7
- Design Excel Sum FormulahardArrayHash TableStringGraph Theory+3frequency 62.7
- Design SpreadsheetmediumArrayHash TableStringDesign+1frequency 62.7
- Design Tic-Tac-ToemediumArrayHash TableDesignMatrix+1frequency 62.7
- Evaluate Reverse Polish NotationmediumArrayMathStackfrequency 62.7
- Length of Longest Subarray With at Most K FrequencymediumArrayHash TableSliding Windowfrequency 62.7
- Max Consecutive Ones IIImediumArrayBinary SearchSliding WindowPrefix Sumfrequency 62.7
- Merge k Sorted ListshardLinked ListDivide and ConquerHeap (Priority Queue)Merge Sort+1frequency 62.7
- Number of IslandsmediumArrayDepth-First SearchBreadth-First SearchUnion-Find+1frequency 62.7
- Reconstruct ItineraryhardArrayStringDepth-First SearchGraph Theory+5frequency 62.7
- Word LadderhardHash TableStringBreadth-First SearchBidirectional Searchfrequency 62.7
- Binary Tree Zigzag Level Order TraversalmediumTreeBreadth-First SearchBinary Treefrequency 55.6
- Count PrimesmediumArrayMathEnumerationNumber Theory+3frequency 55.6
- Group AnagramsmediumArrayHash TableStringSortingfrequency 55.6
- Implement Trie (Prefix Tree)mediumHash TableStringDesignTriefrequency 55.6
- Meeting Rooms IImediumArrayTwo PointersGreedySorting+2frequency 55.6
- Moving Average from Data StreameasyArrayDesignQueueData Streamfrequency 55.6
- Optimal Account BalancinghardArrayDynamic ProgrammingBacktrackingBit Manipulation+1frequency 55.6
- Paint HousemediumArrayDynamic Programmingfrequency 55.6
- Rank Transform of a MatrixhardArrayUnion-FindGraph TheoryTopological Sort+2frequency 55.6