126.Word Ladder II
HardBacktrackingBreadth-First SearchHash Table27.7% acceptance15 companiesVideo
Hard · With video · 67 results
127.Word Ladder
HardBreadth-First SearchHash TableString46.3% acceptance41 companiesVideo
269.Alien Dictionary
HardArrayBreadth-First SearchDepth-First Search37.1% acceptance18 companiesPremium elsewhere, free hereVideo
297.Serialize and Deserialize Binary Tree
HardBinary TreeBreadth-First SearchDepth-First Search61.1% acceptance23 companiesVideo
301.Remove Invalid Parentheses
HardBacktrackingBreadth-First SearchString52.4% acceptance10 companiesVideo
302.Smallest Rectangle Enclosing Black Pixels
HardArrayBinary SearchBreadth-First Search60.9% acceptance1 companyPremium elsewhere, free hereVideo
317.Shortest Distance from All Buildings
HardArrayBreadth-First SearchMatrix44.9% acceptance15 companiesPremium elsewhere, free hereVideo
329.Longest Increasing Path in a Matrix
HardArrayBreadth-First SearchDepth-First Search57.0% acceptance16 companiesVideo
407.Trapping Rain Water II
HardArrayBreadth-First SearchHeap (Priority Queue)64.0% acceptance14 companiesVideo
428.Serialize and Deserialize N-ary Tree
HardBreadth-First SearchDepth-First SearchString68.7% acceptance7 companiesPremium elsewhere, free hereVideo
431.Encode N-ary Tree to Binary Tree
HardBinary TreeBreadth-First SearchDepth-First Search80.6% acceptancePremium elsewhere, free hereVideo
488.Zuma Game
HardBreadth-First SearchDynamic ProgrammingMemoization29.4% acceptance7 companiesVideo
499.The Maze III
HardArrayBreadth-First SearchDepth-First Search52.3% acceptance1 companyPremium elsewhere, free hereVideo
514.Freedom Trail
HardBreadth-First SearchDepth-First SearchDynamic Programming59.4% acceptance3 companiesVideo
675.Cut Off Trees for Golf Event
HardArrayBreadth-First SearchHeap (Priority Queue)36.8% acceptance2 companiesVideo
685.Redundant Connection II
HardBreadth-First SearchDepth-First SearchGraph36.6% acceptance1 companyVideo
711.Number of Distinct Islands II
HardBreadth-First SearchDepth-First SearchHash Function55.3% acceptance2 companiesPremium elsewhere, free hereVideo
749.Contain Virus
HardArrayBreadth-First SearchDepth-First Search56.5% acceptance3 companiesVideo
765.Couples Holding Hands
HardBreadth-First SearchDepth-First SearchGraph59.8% acceptance5 companiesVideo
773.Sliding Puzzle
HardArrayBacktrackingBreadth-First Search74.3% acceptance7 companiesVideo
778.Swim in Rising Water
HardArrayBinary SearchBreadth-First Search68.3% acceptance8 companiesVideo
815.Bus Routes
HardArrayBreadth-First SearchHash Table47.3% acceptance18 companiesVideo
827.Making A Large Island
HardArrayBreadth-First SearchDepth-First Search57.0% acceptance16 companiesVideo
839.Similar String Groups
HardArrayBreadth-First SearchDepth-First Search56.7% acceptance5 companiesVideo
847.Shortest Path Visiting All Nodes
HardBit ManipulationBitmaskBreadth-First Search66.5% acceptance4 companiesVideo
854.K-Similar Strings
HardBreadth-First SearchString41.3% acceptance2 companiesVideo
864.Shortest Path to Get All Keys
HardArrayBit ManipulationBreadth-First Search55.0% acceptance7 companiesVideo
924.Minimize Malware Spread
HardArrayBreadth-First SearchDepth-First Search43.6% acceptance10 companiesVideo
928.Minimize Malware Spread II
HardArrayBreadth-First SearchDepth-First Search46.2% acceptance2 companiesVideo
987.Vertical Order Traversal of a Binary Tree
HardBinary TreeBreadth-First SearchDepth-First Search54.6% acceptance15 companiesVideo
1036.Escape a Large Maze
HardArrayBreadth-First SearchDepth-First Search37.0% acceptance4 companiesVideo
1096.Brace Expansion II
HardBacktrackingBreadth-First SearchStack79.2% acceptance1 companyVideo
1203.Sort Items by Groups Respecting Dependencies
HardBreadth-First SearchDepth-First SearchGraph66.0% acceptance5 companiesVideo
1210.Minimum Moves to Reach Target with Rotations
HardArrayBreadth-First SearchMatrix52.7% acceptance1 companyVideo
1263.Minimum Moves to Move a Box to Their Target Location
HardArrayBreadth-First SearchHeap (Priority Queue)49.7% acceptance1 companyVideo
1284.Minimum Number of Flips to Convert Binary Matrix to Zero Matrix
HardArrayBit ManipulationBreadth-First Search72.9% acceptance1 companyVideo
1293.Shortest Path in a Grid with Obstacles Elimination
HardArrayBreadth-First SearchMatrix46.8% acceptance14 companiesVideo
1298.Maximum Candies You Can Get from Boxes
HardArrayBreadth-First SearchGraph67.2% acceptance4 companiesVideo
1345.Jump Game IV
HardArrayBreadth-First SearchHash Table50.9% acceptance4 companiesVideo
1368.Minimum Cost to Make at Least One Valid Path in a Grid
HardArrayBreadth-First SearchGraph70.9% acceptance8 companiesVideo
1377.Frog Position After T Seconds
HardBreadth-First SearchDepth-First SearchGraph38.8% acceptance2 companiesVideo
1483.Kth Ancestor of a Tree Node
HardBinary SearchBreadth-First SearchDepth-First Search39.7% acceptance3 companiesVideo
1568.Minimum Number of Days to Disconnect Island
HardArrayBreadth-First SearchDepth-First Search58.8% acceptance4 companiesVideo
1970.Last Day Where You Can Still Cross
HardArrayBinary SearchBreadth-First Search68.7% acceptance4 companiesVideo
2045.Second Minimum Time to Reach Destination
HardBreadth-First SearchGraphShortest Path62.3% acceptance1 companyVideo
2092.Find All People With Secret
HardBreadth-First SearchDepth-First SearchGraph48.4% acceptance3 companiesVideo
2204.Distance to a Cycle in Undirected Graph
HardBreadth-First SearchDepth-First SearchGraph73.4% acceptance2 companiesPremium elsewhere, free hereVideo
2258.Escape the Spreading Fire
HardArrayBinary SearchBreadth-First Search39.7% acceptance4 companiesVideo
2290.Minimum Obstacle Removal to Reach Corner
HardArrayBreadth-First SearchGraph71.1% acceptance2 companiesVideo
2328.Number of Increasing Paths in a Grid
HardArrayBreadth-First SearchDepth-First Search57.4% acceptance2 companiesVideo
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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.