Problems
Callback's own problems and the LeetCode questions companies have been asking, in one place — filter by category, company, topic, difficulty, and how recently a question showed up.
Asked on LeetCode
87 questions at Citadel · all time
- Search Suggestions SystemmediumArrayStringBinary SearchTrie+2frequency 55.6
- Sort Items by Groups Respecting DependencieshardDepth-First SearchBreadth-First SearchGraph TheoryTopological Sort+1frequency 55.6
- Sudoku SolverhardArrayHash TableBacktrackingMatrix+2frequency 55.6
- Trapping Rain WaterhardArrayTwo PointersDynamic ProgrammingStack+1frequency 55.6
- Best Time to Buy and Sell Stock IIIhardArrayDynamic Programmingfrequency 45.7
- Best Time to Buy and Sell Stock IVhardArrayDynamic Programmingfrequency 45.7
- Best Time to Buy and Sell Stock with Transaction FeemediumArrayDynamic ProgrammingGreedyfrequency 45.7
- Climbing StairseasyMathDynamic ProgrammingMemoizationfrequency 45.7
- Combination SummediumArrayBacktrackingfrequency 45.7
- Count Number of Maximum Bitwise-OR SubsetsmediumArrayBacktrackingBit ManipulationEnumerationfrequency 45.7
- Course SchedulemediumDepth-First SearchBreadth-First SearchGraph TheoryTopological Sort+1frequency 45.7
- Design A LeaderboardmediumHash TableDesignSortingfrequency 45.7
- Design Front Middle Back QueuemediumArrayLinked ListDesignQueue+2frequency 45.7
- Design In-Memory File SystemhardHash TableStringDesignTrie+1frequency 45.7
- Design Search Autocomplete SystemhardStringDepth-First SearchDesignTrie+3frequency 45.7
- Find Eventual Safe StatesmediumDepth-First SearchBreadth-First SearchGraph TheoryTopological Sort+2frequency 45.7
- Find First and Last Position of Element in Sorted ArraymediumArrayBinary Searchfrequency 45.7
- Knight Probability in ChessboardmediumDynamic Programmingfrequency 45.7
- Koko Eating BananasmediumArrayBinary Searchfrequency 45.7
- Letter Combinations of a Phone NumbermediumHash TableStringBacktrackingfrequency 45.7
- Longest Palindromic SubstringmediumTwo PointersStringDynamic ProgrammingManacherfrequency 45.7
- Max Points on a LinehardArrayHash TableMathGeometry+2frequency 45.7
- Maximum SubarraymediumArrayDivide and ConquerDynamic Programmingfrequency 45.7
- Min StackmediumStackDesignfrequency 45.7
- Next PermutationmediumArrayTwo Pointersfrequency 45.7
- Number of Dice Rolls With Target SummediumDynamic Programmingfrequency 45.7
- Number of Ways to Paint N × 3 GridhardDynamic ProgrammingGraph Coloringfrequency 45.7
- Perfect SquaresmediumMathDynamic ProgrammingBreadth-First SearchKnapsack Problem+1frequency 45.7
- PermutationsmediumArrayBacktrackingfrequency 45.7
- Pow(x, n)mediumMathRecursionfrequency 45.7
- Reorganize StringmediumHash TableStringGreedySorting+2frequency 45.7
- String to Integer (atoi)mediumStringfrequency 45.7
- Transform to ChessboardhardArrayMathBit ManipulationMatrixfrequency 45.7
- Two SumeasyArrayHash Tablefrequency 45.7
- Validate Binary Search TreemediumTreeDepth-First SearchBinary Search TreeBinary Treefrequency 45.7
- Word Ladder IIhardHash TableStringBacktrackingBreadth-First Search+1frequency 45.7
- Word SearchmediumArrayStringBacktrackingDepth-First Search+1frequency 45.7
Listings only — titles, difficulty, and tags link out to LeetCode. Imported from the leetcode-company-wise-problems snapshot dated 1 June 2025. Frequency is that dataset's own relative score within a company and time range.