Problems
Callback's own problems and the LeetCode questions companies have been asking, in one place — pick a category, then filter by company, frequency, status, difficulty, topic, and language.
Asked on LeetCode
3,115 questions · all time
- Longest Substring with At Most K Distinct CharactersmediumHash TableStringSliding Window8 companies
- Convert Sorted Array to Binary Search TreeeasyArrayDivide and ConquerTreeBinary Search Tree+18 companies
- Magnetic Force Between Two BallsmediumArrayBinary SearchSorting8 companies
- Symmetric TreeeasyTreeDepth-First SearchBreadth-First SearchBinary Tree8 companies
- Number of Recent CallseasyDesignQueueData Stream8 companies
- Boundary of Binary TreemediumTreeDepth-First SearchBinary Tree8 companies
- Sparse Matrix MultiplicationmediumArrayHash TableMatrixLinear Algebra8 companies
- Remove ElementeasyArrayTwo Pointers8 companies
- Maximum Frequency StackhardHash TableStackDesignOrdered Set8 companies
- Fibonacci NumbereasyMathDynamic ProgrammingRecursionMemoization8 companies
- Ransom NoteeasyHash TableStringCounting8 companies
- Implement Stack using QueueseasyStackDesignQueue8 companies
- Maximum Width of Binary TreemediumTreeDepth-First SearchBreadth-First SearchBinary Tree8 companies
- Longest Palindromic SubsequencemediumStringDynamic Programming8 companies
- Two Sum II - Input Array Is SortedmediumArrayTwo PointersBinary Search8 companies
- Best Time to Buy and Sell Stock with Transaction FeemediumArrayDynamic ProgrammingGreedy8 companies
- Possible BipartitionmediumDepth-First SearchBreadth-First SearchUnion-FindGraph Theory+28 companies
- Swap Nodes in PairsmediumLinked ListRecursion8 companies
- Delete Node in a BSTmediumTreeBinary Search TreeBinary Tree8 companies
- Same TreeeasyTreeDepth-First SearchBreadth-First SearchBinary Tree8 companies
- Maximal RectanglehardArrayDynamic ProgrammingStackMatrix+18 companies
- Add Two Numbers IImediumLinked ListMathStack8 companies
- Product of the Last K NumbersmediumArrayMathDesignData Stream+18 companies
- Graph Valid TreemediumDepth-First SearchBreadth-First SearchUnion-FindGraph Theory8 companies
- H-IndexmediumArraySortingCounting Sort8 companies
- Coin Change IImediumArrayDynamic ProgrammingKnapsack ProblemComplete Knapsack8 companies
- Put Marbles in BagshardArrayGreedySortingHeap (Priority Queue)8 companies
- Best Time to Buy and Sell Stock IVhardArrayDynamic Programming8 companies
- Amount of Time for Binary Tree to Be InfectedmediumHash TableTreeDepth-First SearchBreadth-First Search+18 companies
- Rearranging FruitshardArrayHash TableGreedySort8 companies
- Path SumeasyTreeDepth-First SearchBreadth-First SearchBinary Tree8 companies
- Swim in Rising WaterhardArrayBinary SearchDepth-First SearchBreadth-First Search+58 companies
- Remove Duplicates from Sorted List IImediumLinked ListTwo Pointers8 companies
- Isomorphic StringseasyHash TableString7 companies
- Minimum Number of Steps to Make Two Strings AnagrammediumHash TableStringCounting7 companies
- Minimum Operations to Reduce an Integer to 0mediumDynamic ProgrammingGreedyBit Manipulation7 companies
- Partition Array Into Two Arrays to Minimize Sum DifferencehardArrayTwo PointersBinary SearchDynamic Programming+57 companies
- Permutation SequencehardMathRecursion7 companies
- Using a Robot to Print the Lexicographically Smallest StringmediumHash TableStringStackGreedy7 companies
- Restore the Array From Adjacent PairsmediumArrayHash TableDepth-First Search7 companies
- Valid Word AbbreviationeasyTwo PointersString7 companies
- Design Authentication ManagermediumHash TableLinked ListDesignDoubly-Linked List7 companies
- Web Crawler MultithreadedmediumDepth-First SearchBreadth-First SearchConcurrency7 companies
- Number of Connected Components in an Undirected GraphmediumDepth-First SearchBreadth-First SearchUnion-FindGraph Theory7 companies
- Remove All Occurrences of a SubstringmediumStringStackSimulation7 companies
- Number of Distinct IslandsmediumArrayHash TableDepth-First SearchBreadth-First Search+47 companies
- Expression Add OperatorshardMathStringBacktracking7 companies
- Subtree of Another TreeeasyTreeDepth-First SearchString MatchingBinary Tree+17 companies
- Design Snake GamemediumArrayHash TableDesignQueue+17 companies
- Contains Duplicate IIIhardArraySliding WindowSortingBucket Sort+17 companies
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.