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
202. Happy Number	Easy	60.0%	Hash Table Math+1	Read
203. Remove Linked List Elements	Easy	55.3%	Linked List Recursion	Read
205. Isomorphic Strings	Easy	48.8%	Hash Table String	Read
206. Reverse Linked List	Easy	81.0%	Linked List Recursion	Read
217. Contains Duplicate	Easy	64.2%	Array Hash Table+1	Read
219. Contains Duplicate II	Easy	51.6%	Array Hash Table+1	Read
225. Implement Stack using Queues	Easy	70.1%	Design Queue+1	Read
226. Invert Binary Tree	Easy	80.5%	Binary Tree Breadth-First Search+2	Read
228. Summary Ranges	Easy	54.6%	Array	Read
231. Power of Two	Easy	50.5%	Bit Manipulation Math+1	Read
232. Implement Queue using Stacks	Easy	70.2%	Design Queue+1	Read
234. Palindrome Linked List	Easy	58.8%	Linked List Recursion+2	Read
242. Valid Anagram	Easy	68.5%	Hash Table Sorting+1	Read
243. Shortest Word Distance	Easy	66.3%	Array String	Read
246. Strobogrammatic Number	Easy	47.6%	Hash Table String+1	Read
252. Meeting Rooms	Easy	59.4%	Array Sorting	Read
257. Binary Tree Paths	Easy	68.9%	Backtracking Binary Tree+3	Read
258. Add Digits	Easy	69.3%	Math Number Theory+1	Read
263. Ugly Number	Easy	43.9%	Math	Read
266. Palindrome Permutation	Easy	68.6%	Bit Manipulation Hash Table+1	Read
268. Missing Number	Easy	72.4%	Array Binary Search+4	Read
270. Closest Binary Search Tree Value	Easy	49.2%	Binary Search Binary Search Tree+3	Read
278. First Bad Version	Easy	47.5%	Binary Search Interactive	Read
283. Move Zeroes	Easy	64.3%	Array Two Pointers	Read
290. Word Pattern	Easy	44.5%	Hash Table String	Read
292. Nim Game	Easy	60.0%	Brainteaser Game Theory+1	Read
293. Flip Game	Easy	64.8%	String	Read
303. Range Sum Query - Immutable	Easy	73.5%	Array Design+1	Read
326. Power of Three	Easy	51.4%	Math Recursion	Read
338. Counting Bits	Easy	80.5%	Bit Manipulation Dynamic Programming	Read
342. Power of Four	Easy	52.5%	Bit Manipulation Math+1	Read
344. Reverse String	Easy	81.2%	String Two Pointers	Read
345. Reverse Vowels of a String	Easy	62.1%	String Two Pointers	Read
346. Moving Average from Data Stream	Easy	80.2%	Array Data Stream+2	Read
349. Intersection of Two Arrays	Easy	78.2%	Array Binary Search+3	Read
350. Intersection of Two Arrays II	Easy	60.4%	Array Binary Search+3	Read
359. Logger Rate Limiter	Easy	76.8%	Data Stream Design+1	Read
367. Valid Perfect Square	Easy	44.8%	Binary Search Math	Read
374. Guess Number Higher or Lower	Easy	57.9%	Binary Search Interactive	Read
383. Ransom Note	Easy	66.3%	Counting Hash Table+1	Read
387. First Unique Character in a String	Easy	66.4%	Counting Hash Table+2	Read
389. Find the Difference	Easy	60.2%	Bit Manipulation Hash Table+2	Read
392. Is Subsequence	Easy	48.9%	Dynamic Programming String+1	Read
401. Binary Watch	Easy	65.9%	Backtracking Bit Manipulation	Read
404. Sum of Left Leaves	Easy	63.1%	Binary Tree Breadth-First Search+2	Read
405. Convert a Number to Hexadecimal	Easy	54.8%	Bit Manipulation Math	Read
408. Valid Word Abbreviation	Easy	37.0%	String Two Pointers	Read
409. Longest Palindrome	Easy	55.9%	Greedy Hash Table+1	Read
412. Fizz Buzz	Easy	75.9%	Math Simulation+1	Read
414. Third Maximum Number	Easy	40.3%	Array Sorting	Read

#202Easy

Happy Number

Hash TableMathTwo Pointers

Acceptance: 60.0%

#203Easy

Remove Linked List Elements

Linked ListRecursion

Acceptance: 55.3%

#205Easy

Isomorphic Strings

Hash TableString

Acceptance: 48.8%

#206Easy

Reverse Linked List

Linked ListRecursion

Acceptance: 81.0%

#217Easy

Contains Duplicate

ArrayHash TableSorting

Acceptance: 64.2%

#219Easy

Contains Duplicate II

ArrayHash TableSliding Window

Acceptance: 51.6%

#225Easy

Implement Stack using Queues

DesignQueueStack

Acceptance: 70.1%

#226Easy

Invert Binary Tree

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 80.5%

#228Easy

Summary Ranges

Array

Acceptance: 54.6%

#231Easy

Power of Two

Bit ManipulationMathRecursion

Acceptance: 50.5%

#232Easy

Implement Queue using Stacks

DesignQueueStack

Acceptance: 70.2%

#234Easy

Palindrome Linked List

Linked ListRecursionStack+1

Acceptance: 58.8%

#242Easy

Valid Anagram

Hash TableSortingString

Acceptance: 68.5%

#243Easy

Shortest Word Distance

ArrayString

Acceptance: 66.3%

#246Easy

Strobogrammatic Number

Hash TableStringTwo Pointers

Acceptance: 47.6%

#252Easy

Meeting Rooms

ArraySorting

Acceptance: 59.4%

#257Easy

Binary Tree Paths

BacktrackingBinary TreeDepth-First Search+2

Acceptance: 68.9%

#258Easy

Add Digits

MathNumber TheorySimulation

Acceptance: 69.3%

#263Easy

Ugly Number

Math

Acceptance: 43.9%

#266Easy

Palindrome Permutation

Bit ManipulationHash TableString

Acceptance: 68.6%

#268Easy

Missing Number

ArrayBinary SearchBit Manipulation+3

Acceptance: 72.4%

#270Easy

Closest Binary Search Tree Value

Binary SearchBinary Search TreeBinary Tree+2

Acceptance: 49.2%

#278Easy

First Bad Version

Binary SearchInteractive

Acceptance: 47.5%

#283Easy

Move Zeroes

ArrayTwo Pointers

Acceptance: 64.3%

#290Easy

Word Pattern

Hash TableString

Acceptance: 44.5%

#292Easy

Nim Game

BrainteaserGame TheoryMath

Acceptance: 60.0%

#293Easy

Flip Game

String

Acceptance: 64.8%

#303Easy

Range Sum Query - Immutable

ArrayDesignPrefix Sum

Acceptance: 73.5%

#326Easy

Power of Three

MathRecursion

Acceptance: 51.4%

#338Easy

Counting Bits

Bit ManipulationDynamic Programming

Acceptance: 80.5%

#342Easy

Power of Four

Bit ManipulationMathRecursion

Acceptance: 52.5%

#344Easy

Reverse String

StringTwo Pointers

Acceptance: 81.2%

#345Easy

Reverse Vowels of a String

StringTwo Pointers

Acceptance: 62.1%

#346Easy

Moving Average from Data Stream

ArrayData StreamDesign+1

Acceptance: 80.2%

#349Easy

Intersection of Two Arrays

ArrayBinary SearchHash Table+2

Acceptance: 78.2%

#350Easy

Intersection of Two Arrays II

ArrayBinary SearchHash Table+2

Acceptance: 60.4%

#359Easy

Logger Rate Limiter

Data StreamDesignHash Table

Acceptance: 76.8%

#367Easy

Valid Perfect Square

Binary SearchMath

Acceptance: 44.8%

#374Easy

Guess Number Higher or Lower

Binary SearchInteractive

Acceptance: 57.9%

#383Easy

Ransom Note

CountingHash TableString

Acceptance: 66.3%

#387Easy

First Unique Character in a String

CountingHash TableQueue+1

Acceptance: 66.4%

#389Easy

Find the Difference

Bit ManipulationHash TableSorting+1

Acceptance: 60.2%

#392Easy

Is Subsequence

Dynamic ProgrammingStringTwo Pointers

Acceptance: 48.9%

#401Easy

Binary Watch

BacktrackingBit Manipulation

Acceptance: 65.9%

#404Easy

Sum of Left Leaves

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 63.1%

#405Easy

Convert a Number to Hexadecimal

Bit ManipulationMath

Acceptance: 54.8%

#408Easy

Valid Word Abbreviation

StringTwo Pointers

Acceptance: 37.0%

#409Easy

Longest Palindrome

GreedyHash TableString

Acceptance: 55.9%

#412Easy

Fizz Buzz

MathSimulationString

Acceptance: 75.9%

#414Easy

Third Maximum Number

ArraySorting

Acceptance: 40.3%

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Master DSA with Step-by-Step Solutions

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