651.4 Keys Keyboard
MediumDynamic ProgrammingMath56.5% acceptance2 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
654.Maximum Binary Tree
MediumArrayBinary TreeDivide and Conquer86.3% acceptance3 companiesVideo
655.Print Binary Tree
MediumBinary TreeBreadth-First SearchDepth-First Search67.1% acceptance5 companiesVideo
656.Coin Path
HardArrayDynamic Programming34.2% acceptance1 companyPremium elsewhere, free hereVideo
657.Robot Return to Origin
EasySimulationString78.0% acceptance5 companiesVideo
658.Find K Closest Elements
MediumArrayBinary SearchHeap (Priority Queue)50.1% acceptance18 companiesVideo
659.Split Array into Consecutive Subsequences
MediumArrayGreedyHash Table52.7% acceptance2 companiesVideo
661.Image Smoother
EasyArrayMatrix69.8% acceptance6 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
664.Strange Printer
HardDynamic ProgrammingString61.0% acceptance9 companiesVideo
665.Non-decreasing Array
MediumArray25.5% acceptance6 companiesVideo
666.Path Sum IV
MediumArrayBinary TreeDepth-First Search63.1% acceptance1 companyPremium elsewhere, free hereVideo
667.Beautiful Arrangement II
MediumArrayMath61.1% acceptance2 companiesVideo
668.Kth Smallest Number in Multiplication Table
HardBinary SearchMath55.1% acceptance5 companiesVideo
669.Trim a Binary Search Tree
MediumBinary Search TreeBinary TreeDepth-First Search66.9% acceptance4 companiesVideo
670.Maximum Swap
MediumGreedyMath51.6% acceptance9 companiesVideo
671.Second Minimum Node In a Binary Tree
EasyBinary TreeDepth-First SearchTree46.0% acceptance2 companiesVideo
672.Bulb Switcher II
MediumBit ManipulationBreadth-First SearchDepth-First Search51.2% acceptance1 companyVideo
673.Number of Longest Increasing Subsequence
MediumArrayBinary Indexed TreeDynamic Programming52.8% acceptance6 companiesVideo
674.Longest Continuous Increasing Subsequence
EasyArray52.5% acceptance5 companiesVideo
675.Cut Off Trees for Golf Event
HardArrayBreadth-First SearchHeap (Priority Queue)36.8% acceptance2 companiesVideo
676.Implement Magic Dictionary
MediumDepth-First SearchDesignHash Table58.4% acceptance2 companiesVideo
677.Map Sum Pairs
MediumDesignHash TableString57.4% acceptance3 companiesVideo
678.Valid Parenthesis String
MediumDynamic ProgrammingGreedyStack42.8% acceptance15 companiesVideo
679.24 Game
HardArrayBacktrackingMath59.4% acceptance7 companiesVideo
680.Valid Palindrome II
EasyGreedyStringTwo Pointers44.7% acceptance16 companiesVideo
681.Next Closest Time
MediumBacktrackingEnumerationHash Table46.8% acceptance1 companyPremium elsewhere, free hereVideo
682.Baseball Game
EasyArraySimulationStack80.8% acceptance6 companiesVideo
683.K Empty Slots
HardArrayBinary Indexed TreeHeap (Priority Queue)38.0% acceptance1 companyPremium elsewhere, free hereVideo
684.Redundant Connection
MediumBreadth-First SearchDepth-First SearchGraph68.0% acceptance8 companiesVideo
685.Redundant Connection II
HardBreadth-First SearchDepth-First SearchGraph36.6% acceptance1 companyVideo
686.Repeated String Match
MediumStringString Matching39.7% acceptance6 companiesVideo
687.Longest Univalue Path
MediumBinary TreeDepth-First SearchTree44.3% acceptance7 companiesVideo
688.Knight Probability in Chessboard
MediumDynamic Programming57.0% acceptance6 companiesVideo
689.Maximum Sum of 3 Non-Overlapping Subarrays
HardArrayDynamic Programming59.8% acceptance6 companiesVideo
690.Employee Importance
MediumArrayBreadth-First SearchDepth-First Search69.4% acceptance6 companiesVideo
691.Stickers to Spell Word
HardArrayBacktrackingBit Manipulation51.3% acceptance4 companiesVideo
692.Top K Frequent Words
MediumBucket SortCountingHash Table60.6% acceptance23 companiesVideo
693.Binary Number with Alternating Bits
EasyBit Manipulation69.8% acceptance5 companiesVideo
694.Number of Distinct Islands
MediumBreadth-First SearchDepth-First SearchHash Function62.8% acceptance12 companiesPremium elsewhere, free hereVideo
695.Max Area of Island
MediumArrayBreadth-First SearchDepth-First Search73.9% acceptance20 companiesVideo
696.Count Binary Substrings
EasyStringTwo Pointers70.3% acceptance18 companiesVideo
697.Degree of an Array
EasyArrayHash Table58.8% acceptance12 companiesVideo
698.Partition to K Equal Sum Subsets
MediumArrayBacktrackingBit Manipulation38.6% acceptance8 companiesVideo
699.Falling Squares
HardArrayOrdered SetSegment Tree48.9% acceptance2 companiesVideo
700.Search in a Binary Search Tree
EasyBinary Search TreeBinary TreeTree83.1% acceptance5 companiesVideo
701.Insert into a Binary Search Tree
MediumBinary Search TreeBinary TreeTree73.6% acceptance7 companiesVideo
Showing 651–700 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.