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
1,399 questions at Meta · all time
- Restore IP AddressesmediumStringBacktrackingfrequency 25.1
- Reverse String IIeasyTwo PointersStringfrequency 25.1
- Strong FriendshipmediumDatabasefrequency 25.1
- Subarray Product Less Than KmediumArrayBinary SearchSliding WindowPrefix Sumfrequency 25.1
- Summary RangeseasyArrayfrequency 25.1
- Top K Frequent WordsmediumArrayHash TableStringTrie+4frequency 25.1
- Total Hamming DistancemediumArrayMathBit Manipulationfrequency 25.1
- Unique Paths IImediumArrayDynamic ProgrammingMatrixfrequency 25.1
- Unique Paths IIIhardArrayBacktrackingBit ManipulationMatrix+1frequency 25.1
- Valid Perfect SquareeasyMathBinary Searchfrequency 25.1
- Validate Binary Tree NodesmediumTreeDepth-First SearchBreadth-First SearchUnion-Find+2frequency 25.1
- Web Crawler MultithreadedmediumDepth-First SearchBreadth-First SearchConcurrencyfrequency 25.1
- Word PatterneasyHash TableStringfrequency 25.1
- Add DigitseasyMathSimulationNumber Theoryfrequency 23.4
- All O`one Data StructurehardHash TableLinked ListDesignDoubly-Linked Listfrequency 23.4
- Apply Discount Every n OrdersmediumArrayHash TableDesignfrequency 23.4
- Balance a Binary Search TreemediumDivide and ConquerGreedyTreeDepth-First Search+2frequency 23.4
- Baseball GameeasyArrayStackSimulationfrequency 23.4
- Best Time to Buy and Sell Stock with Transaction FeemediumArrayDynamic ProgrammingGreedyfrequency 23.4
- Check if the Sentence Is PangrameasyHash TableStringfrequency 23.4
- Construct the Lexicographically Largest Valid SequencemediumArrayBacktrackingfrequency 23.4
- Convert a Number to HexadecimaleasyMathStringBit Manipulationfrequency 23.4
- Count Items Matching a RuleeasyArrayStringfrequency 23.4
- Delete Node in a BSTmediumTreeBinary Search TreeBinary Treefrequency 23.4
- Duplicate EmailseasyDatabasefrequency 23.4
- Element Appearing More Than 25% In Sorted ArrayeasyArrayfrequency 23.4
- Faulty SensoreasyArrayTwo Pointersfrequency 23.4
- Find K Pairs with Smallest SumsmediumArrayHeap (Priority Queue)frequency 23.4
- Find the Kth Smallest Sum of a Matrix With Sorted RowshardArrayBinary SearchHeap (Priority Queue)Matrixfrequency 23.4
- Get Highest Answer Rate QuestionmediumDatabasefrequency 23.4
- Inorder Successor in BST IImediumTreeBinary Search TreeBinary Treefrequency 23.4
- Invalid TweetseasyDatabasefrequency 23.4
- Investments in 2016mediumDatabasefrequency 23.4
- Longest PalindromeeasyHash TableStringGreedyfrequency 23.4
- Longest Palindromic SubsequencemediumStringDynamic Programmingfrequency 23.4
- Maximum Binary Tree IImediumTreeBinary Treefrequency 23.4
- Maximum Level Sum of a Binary TreemediumTreeDepth-First SearchBreadth-First SearchBinary Treefrequency 23.4
- Maximum Points You Can Obtain from CardsmediumArraySliding WindowPrefix Sumfrequency 23.4
- Minimum Cost Path with Edge ReversalsmediumGraph TheoryHeap (Priority Queue)Shortest Pathfrequency 23.4
- Minimum Depth of Binary TreeeasyTreeDepth-First SearchBreadth-First SearchBinary Treefrequency 23.4
- Minimum Swaps To Make Sequences IncreasinghardArrayDynamic Programmingfrequency 23.4
- Number of Visible People in a QueuehardArrayStackMonotonic Stackfrequency 23.4
- Number of Ways to Arrive at DestinationmediumDynamic ProgrammingGraph TheoryTopological SortShortest Path+1frequency 23.4
- Open the LockmediumArrayHash TableStringBreadth-First Search+1frequency 23.4
- Pacific Atlantic Water FlowmediumArrayDepth-First SearchBreadth-First SearchMatrixfrequency 23.4
- Paint House IIhardArrayDynamic Programmingfrequency 23.4
- Path SumeasyTreeDepth-First SearchBreadth-First SearchBinary Treefrequency 23.4
- Prefix and Suffix SearchhardArrayHash TableStringDesign+1frequency 23.4
- Product Price at a Given DatemediumDatabasefrequency 23.4
- Product of the Last K NumbersmediumArrayMathDesignData Stream+1frequency 23.4
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.