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.
Solve on Callback
7 problems asked at Amazon — full prompts you can work right here.
Pair Sum in a Sorted Array
Algorithms & Data Structures · The two-pointer warm-up every loop still asks.
Design an LRU Cache
Algorithms & Data Structures · Hash map plus doubly linked list, all operations O(1).
Top Earners per Department
SQL & Data · Window functions beat self-joins — know why.
Design a Rate Limiter
System Design · Token bucket, sliding window, and where the counters live.
Tell Me About a Conflict
Behavioral · STAR structure for the most common behavioral prompt.
Build a Todo List
Frontend · List state done right: keys, controlled input, and deletes.
Build an Accordion
Frontend · Independent toggles — a Set of open ids, not N booleans.
Asked on LeetCode
2,011 questions at Amazon · all time
- Two SumeasyArrayHash Tablefrequency 100.0
- LRU CachemediumHash TableLinked ListDesignDoubly-Linked Listfrequency 88.5
- Trapping Rain WaterhardArrayTwo PointersDynamic ProgrammingStack+1frequency 88.0
- Number of IslandsmediumArrayDepth-First SearchBreadth-First SearchUnion-Find+1frequency 85.6
- Longest Substring Without Repeating CharactersmediumHash TableStringSliding Windowfrequency 84.5
- Best Time to Buy and Sell StockeasyArrayDynamic Programmingfrequency 83.8
- Group AnagramsmediumArrayHash TableStringSortingfrequency 80.6
- Add Two NumbersmediumLinked ListMathRecursionfrequency 79.7
- Longest Palindromic SubstringmediumTwo PointersStringDynamic ProgrammingManacherfrequency 78.5
- 3SummediumArrayTwo PointersSortingfrequency 78.3
- Reorganize StringmediumHash TableStringGreedySorting+2frequency 78.3
- Median of Two Sorted ArrayshardArrayBinary SearchDivide and Conquerfrequency 76.8
- Container With Most WatermediumArrayTwo PointersGreedyfrequency 76.7
- Merge IntervalsmediumArraySortingQuicksortfrequency 76.6
- Course SchedulemediumDepth-First SearchBreadth-First SearchGraph TheoryTopological Sort+1frequency 75.0
- Koko Eating BananasmediumArrayBinary Searchfrequency 74.9
- Valid ParentheseseasyStringStackBracket Sequencesfrequency 74.4
- Merge k Sorted ListshardLinked ListDivide and ConquerHeap (Priority Queue)Merge Sort+1frequency 73.9
- Rotting OrangesmediumArrayBreadth-First SearchMatrixfrequency 73.9
- Longest Common PrefixeasyArrayStringTriefrequency 73.0
- Subarray Sum Equals KmediumArrayHash TablePrefix Sumfrequency 72.9
- Maximum SubarraymediumArrayDivide and ConquerDynamic Programmingfrequency 72.0
- Top K Frequent ElementsmediumArrayHash TableDivide and ConquerSorting+4frequency 71.7
- Search in Rotated Sorted ArraymediumArrayBinary Searchfrequency 71.6
- Merge Sorted ArrayeasyArrayTwo PointersSortingfrequency 70.9
- Palindrome NumbereasyMathfrequency 70.8
- Longest Consecutive SequencemediumArrayHash TableUnion-Findfrequency 70.7
- Lowest Common Ancestor of a Binary TreemediumTreeDepth-First SearchBinary TreeBinary Lifting+1frequency 69.9
- Copy List with Random PointermediumHash TableLinked Listfrequency 69.8
- Majority ElementeasyArrayHash TableDivide and ConquerSorting+2frequency 69.6
- Generate ParenthesesmediumStringDynamic ProgrammingBacktrackingBracket Sequencesfrequency 69.1
- Word LadderhardHash TableStringBreadth-First SearchBidirectional Searchfrequency 68.3
- Jump GamemediumArrayDynamic ProgrammingGreedyfrequency 67.9
- Product of Array Except SelfmediumArrayPrefix Sumfrequency 67.5
- House RobbermediumArrayDynamic Programmingfrequency 67.3
- Climbing StairseasyMathDynamic ProgrammingMemoizationfrequency 67.0
- Letter Combinations of a Phone NumbermediumHash TableStringBacktrackingfrequency 66.9
- Merge Two Sorted ListseasyLinked ListRecursionfrequency 66.7
- Course Schedule IImediumDepth-First SearchBreadth-First SearchGraph TheoryTopological Sortfrequency 65.8
- Sliding Window MaximumhardArrayQueueSliding WindowHeap (Priority Queue)+2frequency 65.6
- Spiral MatrixmediumArrayMatrixSimulationfrequency 65.3
- Word SearchmediumArrayStringBacktrackingDepth-First Search+1frequency 65.3
- Valid AnagrameasyHash TableStringSortingfrequency 64.3
- SubsetsmediumArrayBacktrackingBit Manipulationfrequency 64.0
- Fruit Into BasketsmediumArrayHash TableSliding Windowfrequency 63.6
- Remove Duplicates from Sorted ArrayeasyArrayTwo Pointersfrequency 63.6
- Rotate ImagemediumArrayMathMatrixfrequency 63.5
- Next PermutationmediumArrayTwo Pointersfrequency 63.3
- Coin ChangemediumArrayDynamic ProgrammingBreadth-First SearchKnapsack Problem+1frequency 63.1
- Find Median from Data StreamhardTwo PointersDesignSortingHeap (Priority Queue)+1frequency 63.1
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.