Solutions & Explanations

Browse 4,029+ detailed solutions with multiple approaches, code in Python, Java, C++ and more.

4,029 Solutions961 Easy2102 Medium966 Hard

Title	Difficulty	Acceptance	Topics	Solution
651. 4 Keys Keyboard	Medium	56.5%	Dynamic Programming Math	Read
652. Find Duplicate Subtrees	Medium	60.6%	Binary Tree Depth-First Search+2	Read
653. Two Sum IV - Input is a BST	Easy	63.7%	Binary Search Tree Binary Tree+5	Read
654. Maximum Binary Tree	Medium	86.3%	Array Binary Tree+4	Read
655. Print Binary Tree	Medium	66.5%	Binary Tree Breadth-First Search+2	Read
656. Coin Path	Hard	34.2%	Array Dynamic Programming	Read
657. Robot Return to Origin	Easy	78.0%	Simulation String	Read
658. Find K Closest Elements	Medium	50.1%	Array Binary Search+4	Read
659. Split Array into Consecutive Subsequences	Medium	52.1%	Array Greedy+2	Read
660. Remove 9	Hard	57.3%	Math	Read
661. Image Smoother	Easy	69.8%	Array Matrix	Read
662. Maximum Width of Binary Tree	Medium	46.0%	Binary Tree Breadth-First Search+2	Read
663. Equal Tree Partition	Medium	42.3%	Binary Tree Depth-First Search+1	Read
664. Strange Printer	Hard	61.0%	Dynamic Programming String	Read
665. Non-decreasing Array	Medium	25.5%	Array	Read
666. Path Sum IV	Medium	62.5%	Array Binary Tree+3	Read
667. Beautiful Arrangement II	Medium	61.1%	Array Math	Read
668. Kth Smallest Number in Multiplication Table	Hard	54.5%	Binary Search Math	Read
669. Trim a Binary Search Tree	Medium	66.9%	Binary Search Tree Binary Tree+2	Read
670. Maximum Swap	Medium	51.6%	Greedy Math	Read
671. Second Minimum Node In a Binary Tree	Easy	46.0%	Binary Tree Depth-First Search+1	Read
672. Bulb Switcher II	Medium	50.6%	Bit Manipulation Breadth-First Search+2	Read
673. Number of Longest Increasing Subsequence	Medium	52.2%	Array Binary Indexed Tree+2	Read
674. Longest Continuous Increasing Subsequence	Easy	51.9%	Array	Read
675. Cut Off Trees for Golf Event	Hard	36.8%	Array Breadth-First Search+2	Read
676. Implement Magic Dictionary	Medium	57.8%	Depth-First Search Design+3	Read
677. Map Sum Pairs	Medium	57.4%	Design Hash Table+2	Read
678. Valid Parenthesis String	Medium	40.5%	Dynamic Programming Greedy+2	Read
679. 24 Game	Hard	59.4%	Array Backtracking+1	Read
680. Valid Palindrome II	Easy	44.7%	Greedy String+1	Read
681. Next Closest Time	Medium	46.8%	Backtracking Enumeration+2	Read
682. Baseball Game	Easy	80.8%	Array Simulation+1	Read
683. K Empty Slots	Hard	38.0%	Array Binary Indexed Tree+6	Read
684. Redundant Connection	Medium	68.0%	Breadth-First Search Depth-First Search+2	Read
685. Redundant Connection II	Hard	36.6%	Breadth-First Search Depth-First Search+2	Read
686. Repeated String Match	Medium	39.7%	String String Matching	Read
687. Longest Univalue Path	Medium	44.3%	Binary Tree Depth-First Search+1	Read
688. Knight Probability in Chessboard	Medium	57.0%	Dynamic Programming	Read
689. Maximum Sum of 3 Non-Overlapping Subarrays	Hard	59.8%	Array Dynamic Programming	Read
690. Employee Importance	Medium	69.4%	Array Breadth-First Search+3	Read
691. Stickers to Spell Word	Hard	50.7%	Array Backtracking+4	Read
692. Top K Frequent Words	Medium	60.6%	Bucket Sort Counting+5	Read
693. Binary Number with Alternating Bits	Easy	69.8%	Bit Manipulation	Read
694. Number of Distinct Islands	Medium	62.8%	Breadth-First Search Depth-First Search+3	Read
695. Max Area of Island	Medium	73.9%	Array Breadth-First Search+3	Read
696. Count Binary Substrings	Easy	70.3%	String Two Pointers	Read
697. Degree of an Array	Easy	58.2%	Array Hash Table	Read
698. Partition to K Equal Sum Subsets	Medium	38.6%	Array Backtracking+4	Read
699. Falling Squares	Hard	48.3%	Array Ordered Set+1	Read
700. Search in a Binary Search Tree	Easy	83.1%	Binary Search Tree Binary Tree+1	Read

#651Medium

4 Keys Keyboard

Dynamic ProgrammingMath

Acceptance: 56.5%

#652Medium

Find Duplicate Subtrees

Binary TreeDepth-First SearchHash Table+1

Acceptance: 60.6%

#653Easy

Two Sum IV - Input is a BST

Binary Search TreeBinary TreeBreadth-First Search+4

Acceptance: 63.7%

#654Medium

Maximum Binary Tree

ArrayBinary TreeDivide and Conquer+3

Acceptance: 86.3%

#655Medium

Print Binary Tree

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 66.5%

#656Hard

Coin Path

ArrayDynamic Programming

Acceptance: 34.2%

#657Easy

Robot Return to Origin

SimulationString

Acceptance: 78.0%

#658Medium

Find K Closest Elements

ArrayBinary SearchHeap (Priority Queue)+3

Acceptance: 50.1%

#659Medium

Split Array into Consecutive Subsequences

ArrayGreedyHash Table+1

Acceptance: 52.1%

#660Hard

Remove 9

Math

Acceptance: 57.3%

#661Easy

Image Smoother

ArrayMatrix

Acceptance: 69.8%

#662Medium

Maximum Width of Binary Tree

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 46.0%

#663Medium

Equal Tree Partition

Binary TreeDepth-First SearchTree

Acceptance: 42.3%

#664Hard

Strange Printer

Dynamic ProgrammingString

Acceptance: 61.0%

#665Medium

Non-decreasing Array

Array

Acceptance: 25.5%

#666Medium

Path Sum IV

ArrayBinary TreeDepth-First Search+2

Acceptance: 62.5%

#667Medium

Beautiful Arrangement II

ArrayMath

Acceptance: 61.1%

#668Hard

Kth Smallest Number in Multiplication Table

Binary SearchMath

Acceptance: 54.5%

#669Medium

Trim a Binary Search Tree

Binary Search TreeBinary TreeDepth-First Search+1

Acceptance: 66.9%

#670Medium

Maximum Swap

GreedyMath

Acceptance: 51.6%

#671Easy

Second Minimum Node In a Binary Tree

Binary TreeDepth-First SearchTree

Acceptance: 46.0%

#672Medium

Bulb Switcher II

Bit ManipulationBreadth-First SearchDepth-First Search+1

Acceptance: 50.6%

#673Medium

Number of Longest Increasing Subsequence

ArrayBinary Indexed TreeDynamic Programming+1

Acceptance: 52.2%

#674Easy

Longest Continuous Increasing Subsequence

Array

Acceptance: 51.9%

#675Hard

Cut Off Trees for Golf Event

ArrayBreadth-First SearchHeap (Priority Queue)+1

Acceptance: 36.8%

#676Medium

Implement Magic Dictionary

Depth-First SearchDesignHash Table+2

Acceptance: 57.8%

#677Medium

Map Sum Pairs

DesignHash TableString+1

Acceptance: 57.4%

#678Medium

Valid Parenthesis String

Dynamic ProgrammingGreedyStack+1

Acceptance: 40.5%

#679Hard

24 Game

ArrayBacktrackingMath

Acceptance: 59.4%

#680Easy

Valid Palindrome II

GreedyStringTwo Pointers

Acceptance: 44.7%

#681Medium

Next Closest Time

BacktrackingEnumerationHash Table+1

Acceptance: 46.8%

#682Easy

Baseball Game

ArraySimulationStack

Acceptance: 80.8%

#683Hard

K Empty Slots

ArrayBinary Indexed TreeHeap (Priority Queue)+5

Acceptance: 38.0%

#684Medium

Redundant Connection

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 68.0%

#685Hard

Redundant Connection II

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 36.6%

#686Medium

Repeated String Match

StringString Matching

Acceptance: 39.7%

#687Medium

Longest Univalue Path

Binary TreeDepth-First SearchTree

Acceptance: 44.3%

#688Medium

Knight Probability in Chessboard

Dynamic Programming

Acceptance: 57.0%

#689Hard

Maximum Sum of 3 Non-Overlapping Subarrays

ArrayDynamic Programming

Acceptance: 59.8%

#690Medium

Employee Importance

ArrayBreadth-First SearchDepth-First Search+2

Acceptance: 69.4%

#691Hard

Stickers to Spell Word

ArrayBacktrackingBit Manipulation+3

Acceptance: 50.7%

#692Medium

Top K Frequent Words

Bucket SortCountingHash Table+4

Acceptance: 60.6%

#693Easy

Binary Number with Alternating Bits

Bit Manipulation

Acceptance: 69.8%

#694Medium

Number of Distinct Islands

Breadth-First SearchDepth-First SearchHash Function+2

Acceptance: 62.8%

#695Medium

Max Area of Island

ArrayBreadth-First SearchDepth-First Search+2

Acceptance: 73.9%

#696Easy

Count Binary Substrings

StringTwo Pointers

Acceptance: 70.3%

#697Easy

Degree of an Array

ArrayHash Table

Acceptance: 58.2%

#698Medium

Partition to K Equal Sum Subsets

ArrayBacktrackingBit Manipulation+3

Acceptance: 38.6%

#699Hard

Falling Squares

ArrayOrdered SetSegment Tree

Acceptance: 48.3%

#700Easy

Search in a Binary Search Tree

Binary Search TreeBinary TreeTree

Acceptance: 83.1%

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Master DSA with Step-by-Step Solutions

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