251.Flatten 2D Vector
MediumArrayDesignIterator50.5% acceptance4 companiesPremium elsewhere, free hereVideo
252.Meeting Rooms
EasyArraySorting59.4% acceptance10 companiesPremium elsewhere, free hereVideo
253.Meeting Rooms II
MediumArrayGreedyHeap (Priority Queue)52.6% acceptance42 companiesPremium elsewhere, free hereVideo
254.Factor Combinations
MediumBacktracking50.5% acceptance2 companiesPremium elsewhere, free hereVideo
255.Verify Preorder Sequence in Binary Search Tree
MediumArrayBinary Search TreeBinary Tree51.7% acceptance5 companiesPremium elsewhere, free hereVideo
256.Paint House
MediumArrayDynamic Programming64.3% acceptance8 companiesPremium elsewhere, free hereVideo
257.Binary Tree Paths
EasyBacktrackingBinary TreeDepth-First Search69.5% acceptance8 companiesVideo
258.Add Digits
EasyMathNumber TheorySimulation69.3% acceptance10 companiesVideo
259.3Sum Smaller
MediumArrayBinary SearchSorting51.4% acceptance7 companiesPremium elsewhere, free hereVideo
260.Single Number III
MediumArrayBit Manipulation70.2% acceptance7 companiesVideo
261.Graph Valid Tree
MediumBreadth-First SearchDepth-First SearchGraph49.9% acceptance9 companiesPremium elsewhere, free hereVideo
262.Trips and Users
HardDatabase39.4% acceptance5 companiesVideo
263.Ugly Number
EasyMath43.9% acceptance8 companiesVideo
264.Ugly Number II
MediumDynamic ProgrammingHash TableHeap (Priority Queue)49.7% acceptance9 companiesVideo
265.Paint House II
HardArrayDynamic Programming57.0% acceptance2 companiesPremium elsewhere, free hereVideo
266.Palindrome Permutation
EasyBit ManipulationHash TableString68.6% acceptance5 companiesPremium elsewhere, free hereVideo
267.Palindrome Permutation II
MediumBacktrackingHash TableString41.9% acceptancePremium elsewhere, free hereVideo
268.Missing Number
EasyArrayBinary SearchBit Manipulation72.4% acceptance19 companiesVideo
269.Alien Dictionary
HardArrayBreadth-First SearchDepth-First Search37.1% acceptance18 companiesPremium elsewhere, free hereVideo
270.Closest Binary Search Tree Value
EasyBinary SearchBinary Search TreeBinary Tree49.2% acceptance7 companiesPremium elsewhere, free hereVideo
271.Encode and Decode Strings
MediumArrayDesignString51.9% acceptance11 companiesPremium elsewhere, free hereVideo
272.Closest Binary Search Tree Value II
HardBinary Search TreeBinary TreeDepth-First Search61.1% acceptance3 companiesPremium elsewhere, free hereVideo
273.Integer to English Words
HardMathRecursionString34.9% acceptance24 companiesVideo
274.H-Index
MediumArrayCounting SortSorting41.8% acceptance8 companiesVideo
275.H-Index II
MediumArrayBinary Search40.0% acceptance1 companyVideo
276.Paint Fence
MediumDynamic Programming48.3% acceptance4 companiesPremium elsewhere, free hereVideo
277.Find the Celebrity
MediumGraphInteractiveTwo Pointers48.9% acceptance12 companiesPremium elsewhere, free hereVideo
278.First Bad Version
EasyBinary SearchInteractive47.5% acceptance7 companiesVideo
279.Perfect Squares
MediumBreadth-First SearchDynamic ProgrammingMath57.0% acceptance12 companiesVideo
280.Wiggle Sort
MediumArrayGreedySorting68.5% acceptance4 companiesPremium elsewhere, free hereVideo
281.Zigzag Iterator
MediumArrayDesignIterator67.1% acceptance5 companiesPremium elsewhere, free hereVideo
282.Expression Add Operators
HardBacktrackingMathString43.5% acceptance7 companiesVideo
283.Move Zeroes
EasyArrayTwo Pointers64.3% acceptance46 companiesVideo
284.Peeking Iterator
MediumArrayDesignIterator61.9% acceptance3 companiesVideo
285.Inorder Successor in BST
MediumBinary Search TreeBinary TreeDepth-First Search51.2% acceptance6 companiesPremium elsewhere, free hereVideo
286.Walls and Gates
MediumArrayBreadth-First SearchMatrix63.9% acceptance11 companiesPremium elsewhere, free hereVideo
287.Find the Duplicate Number
MediumArrayBinary SearchBit Manipulation64.7% acceptance22 companiesVideo
288.Unique Word Abbreviation
MediumArrayDesignHash Table28.1% acceptance1 companyPremium elsewhere, free hereVideo
289.Game of Life
MediumArrayMatrixSimulation73.0% acceptance15 companiesVideo
290.Word Pattern
EasyHash TableString44.5% acceptance9 companiesVideo
291.Word Pattern II
MediumBacktrackingHash TableString49.1% acceptance6 companiesPremium elsewhere, free hereVideo
292.Nim Game
EasyBrainteaserGame TheoryMath60.6% acceptance6 companiesVideo
293.Flip Game
EasyString64.8% acceptance1 companyPremium elsewhere, free hereVideo
294.Flip Game II
MediumBacktrackingDynamic ProgrammingGame Theory52.2% acceptance2 companiesPremium elsewhere, free hereVideo
295.Find Median from Data Stream
HardData StreamDesignHeap (Priority Queue)54.9% acceptance40 companiesVideo
296.Best Meeting Point
HardArrayMathMatrix61.1% acceptance9 companiesPremium elsewhere, free hereVideo
297.Serialize and Deserialize Binary Tree
HardBinary TreeBreadth-First SearchDepth-First Search61.1% acceptance23 companiesVideo
298.Binary Tree Longest Consecutive Sequence
MediumBinary TreeDepth-First SearchTree54.7% acceptance4 companiesPremium elsewhere, free hereVideo
299.Bulls and Cows
MediumCountingHash TableString52.9% acceptance7 companiesVideo
300.Longest Increasing Subsequence
MediumArrayBinary SearchDynamic Programming59.8% acceptance30 companiesVideo
Showing 251–300 of 3,918
How to use these solutions
Each solution breaks the problem into approaches, usually from brute force to the best one, and explains why each works. Code comes in Python, Java, C++ and other languages. Knowing why an approach works matters more in an interview than remembering the code.
- Try the problem first. Give it at least 20 minutes before you open the solution.
- Read every approach. The brute force shows you the problem; the faster ones show the pattern.
- Check the complexity. Note the time and space of each approach and what makes the difference.
- Write it yourself. Close the solution and code it from memory in the editor.
- Come back in a week. Solving it again later is what makes the pattern stick.