366.Find Leaves of Binary Tree
MediumBinary TreeDepth-First SearchTree81.4% acceptance6 companiesPremium elsewhere, free hereVideo
321 results
385.Mini Parser
MediumDepth-First SearchStackString44.0% acceptance4 companiesVideo
386.Lexicographical Numbers
MediumDepth-First SearchTrie76.2% acceptance6 companiesVideo
388.Longest Absolute File Path
MediumDepth-First SearchStackString49.9% acceptance4 companiesVideo
399.Evaluate Division
MediumArrayBreadth-First SearchDepth-First Search64.7% acceptance23 companiesVideo
404.Sum of Left Leaves
EasyBinary TreeBreadth-First SearchDepth-First Search63.1% acceptance6 companiesVideo
417.Pacific Atlantic Water Flow
MediumArrayBreadth-First SearchDepth-First Search61.3% acceptance11 companiesVideo
419.Battleships in a Board
MediumArrayDepth-First SearchMatrix77.4% acceptance8 companiesVideo
426.Convert Binary Search Tree to Sorted Doubly Linked List
MediumBinary Search TreeBinary TreeDepth-First Search65.2% acceptance4 companiesPremium elsewhere, free hereVideo
428.Serialize and Deserialize N-ary Tree
HardBreadth-First SearchDepth-First SearchString68.7% acceptance7 companiesPremium elsewhere, free hereVideo
430.Flatten a Multilevel Doubly Linked List
MediumDepth-First SearchDoubly-Linked ListLinked List63.3% acceptance6 companiesVideo
431.Encode N-ary Tree to Binary Tree
HardBinary TreeBreadth-First SearchDepth-First Search80.6% acceptancePremium elsewhere, free hereVideo
437.Path Sum III
MediumBinary TreeDepth-First SearchTree46.6% acceptance11 companiesVideo
449.Serialize and Deserialize BST
MediumBinary Search TreeBinary TreeBreadth-First Search60.1% acceptance4 companiesVideo
463.Island Perimeter
EasyArrayBreadth-First SearchDepth-First Search74.3% acceptance9 companiesVideo
472.Concatenated Words
HardArrayDepth-First SearchDynamic Programming49.9% acceptance3 companiesVideo
490.The Maze
MediumArrayBreadth-First SearchDepth-First Search60.4% acceptance13 companiesPremium elsewhere, free hereVideo
499.The Maze III
HardArrayBreadth-First SearchDepth-First Search52.3% acceptance1 companyPremium elsewhere, free hereVideo
501.Find Mode in Binary Search Tree
EasyBinary Search TreeBinary TreeDepth-First Search59.2% acceptance4 companiesVideo
505.The Maze II
MediumArrayBreadth-First SearchDepth-First Search55.0% acceptance5 companiesPremium elsewhere, free hereVideo
508.Most Frequent Subtree Sum
MediumBinary TreeDepth-First SearchHash Table69.6% acceptance3 companiesVideo
513.Find Bottom Left Tree Value
MediumBinary TreeBreadth-First SearchDepth-First Search72.2% acceptance7 companiesVideo
514.Freedom Trail
HardBreadth-First SearchDepth-First SearchDynamic Programming59.4% acceptance3 companiesVideo
515.Find Largest Value in Each Tree Row
MediumBinary TreeBreadth-First SearchDepth-First Search66.3% acceptance8 companiesVideo
529.Minesweeper
MediumArrayBreadth-First SearchDepth-First Search68.7% acceptance9 companiesVideo
530.Minimum Absolute Difference in BST
EasyBinary Search TreeBinary TreeBreadth-First Search59.3% acceptance3 companiesVideo
536.Construct Binary Tree from String
MediumBinary TreeDepth-First SearchStack58.7% acceptance3 companiesPremium elsewhere, free hereVideo
538.Convert BST to Greater Tree
MediumBinary Search TreeBinary TreeDepth-First Search72.1% acceptance4 companiesVideo
543.Diameter of Binary Tree
EasyBinary TreeDepth-First SearchTree66.4% acceptance20 companiesVideo
545.Boundary of Binary Tree
MediumBinary TreeDepth-First SearchTree48.0% acceptance10 companiesPremium elsewhere, free hereVideo
547.Number of Provinces
MediumBreadth-First SearchDepth-First SearchGraph70.8% acceptance9 companiesVideo
549.Binary Tree Longest Consecutive Sequence II
MediumBinary TreeDepth-First SearchTree50.1% acceptance3 companiesPremium elsewhere, free hereVideo
559.Maximum Depth of N-ary Tree
EasyBreadth-First SearchDepth-First SearchTree73.5% acceptance2 companiesVideo
563.Binary Tree Tilt
EasyBinary TreeDepth-First SearchTree66.2% acceptance3 companiesVideo
565.Array Nesting
MediumArrayDepth-First Search56.6% acceptance3 companiesVideo
572.Subtree of Another Tree
EasyBinary TreeDepth-First SearchHash Function52.0% acceptance8 companiesVideo
582.Kill Process
MediumArrayBreadth-First SearchDepth-First Search70.4% acceptance4 companiesPremium elsewhere, free hereVideo
589.N-ary Tree Preorder Traversal
EasyDepth-First SearchStackTree76.7% acceptance2 companiesVideo
590.N-ary Tree Postorder Traversal
EasyDepth-First SearchStackTree81.0% acceptance3 companiesVideo
606.Construct String from Binary Tree
MediumBinary TreeDepth-First SearchString70.6% acceptance3 companiesVideo
617.Merge Two Binary Trees
EasyBinary TreeBreadth-First SearchDepth-First Search79.2% acceptance8 companiesVideo
623.Add One Row to Tree
MediumBinary TreeBreadth-First SearchDepth-First Search64.1% acceptance3 companiesVideo
637.Average of Levels in Binary Tree
EasyBinary TreeBreadth-First SearchDepth-First Search74.8% acceptance4 companiesVideo
642.Design Search Autocomplete System
HardData StreamDepth-First SearchDesign49.9% acceptance12 companiesPremium elsewhere, free hereVideo
652.Find Duplicate Subtrees
MediumBinary TreeDepth-First SearchHash Table60.6% acceptance8 companiesVideo
653.Two Sum IV - Input is a BST
EasyBinary Search TreeBinary TreeBreadth-First Search63.7% acceptance8 companiesVideo
655.Print Binary Tree
MediumBinary TreeBreadth-First SearchDepth-First Search67.1% acceptance5 companiesVideo
662.Maximum Width of Binary Tree
MediumBinary TreeBreadth-First SearchDepth-First Search46.0% acceptance8 companiesVideo
663.Equal Tree Partition
MediumBinary TreeDepth-First SearchTree42.3% acceptance1 companyPremium elsewhere, free hereVideo
666.Path Sum IV
MediumArrayBinary TreeDepth-First Search63.1% acceptance1 companyPremium elsewhere, free hereVideo
Showing 51–100 of 321
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.