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
301. Remove Invalid Parentheses	Hard	49.8%	Backtracking Breadth-First Search+1	Read
302. Smallest Rectangle Enclosing Black Pixels	Hard	60.9%	Array Binary Search+3	Read
303. Range Sum Query - Immutable	Easy	73.5%	Array Design+1	Read
304. Range Sum Query 2D - Immutable	Medium	58.6%	Array Design+2	Read
305. Number of Islands II	Hard	40.5%	Array Hash Table+1	Read
306. Additive Number	Medium	34.2%	Backtracking String	Read
307. Range Sum Query - Mutable	Medium	43.3%	Array Binary Indexed Tree+2	Read
308. Range Sum Query 2D - Mutable	Medium	46.0%	Array Binary Indexed Tree+3	Read
309. Best Time to Buy and Sell Stock with Cooldown	Medium	62.4%	Array Dynamic Programming	Read
310. Minimum Height Trees	Medium	42.4%	Breadth-First Search Depth-First Search+2	Read
311. Sparse Matrix Multiplication	Medium	69.3%	Array Hash Table+1	Read
312. Burst Balloons	Hard	64.3%	Array Dynamic Programming	Read
313. Super Ugly Number	Medium	46.6%	Array Dynamic Programming+1	Read
314. Binary Tree Vertical Order Traversal	Medium	57.8%	Binary Tree Breadth-First Search+4	Read
315. Count of Smaller Numbers After Self	Hard	44.0%	Array Binary Indexed Tree+5	Read
316. Remove Duplicate Letters	Medium	54.1%	Greedy Monotonic Stack+2	Read
317. Shortest Distance from All Buildings	Hard	44.9%	Array Breadth-First Search+1	Read
318. Maximum Product of Word Lengths	Medium	61.1%	Array Bit Manipulation+1	Read
319. Bulb Switcher	Medium	56.2%	Brainteaser Math	Read
320. Generalized Abbreviation	Medium	60.4%	Backtracking Bit Manipulation+1	Read
321. Create Maximum Number	Hard	36.7%	Array Greedy+3	Read
322. Coin Change	Medium	48.7%	Array Breadth-First Search+1	Read
323. Number of Connected Components in an Undirected Graph	Medium	64.9%	Breadth-First Search Depth-First Search+2	Read
324. Wiggle Sort II	Medium	38.4%	Array Divide and Conquer+3	Read
325. Maximum Size Subarray Sum Equals k	Medium	50.8%	Array Hash Table+1	Read
326. Power of Three	Easy	51.4%	Math Recursion	Read
327. Count of Range Sum	Hard	39.7%	Array Binary Indexed Tree+5	Read
328. Odd Even Linked List	Medium	62.4%	Linked List	Read
329. Longest Increasing Path in a Matrix	Hard	57.0%	Array Breadth-First Search+6	Read
330. Patching Array	Hard	54.7%	Array Greedy	Read
331. Verify Preorder Serialization of a Binary Tree	Medium	47.8%	Binary Tree Stack+2	Read
332. Reconstruct Itinerary	Hard	45.0%	Depth-First Search Eulerian Circuit+1	Read
333. Largest BST Subtree	Medium	45.8%	Binary Search Tree Binary Tree+3	Read
334. Increasing Triplet Subsequence	Medium	39.3%	Array Greedy	Read
335. Self Crossing	Hard	36.3%	Array Geometry+1	Read
336. Palindrome Pairs	Hard	37.1%	Array Hash Table+2	Read
337. House Robber III	Medium	56.3%	Binary Tree Depth-First Search+2	Read
338. Counting Bits	Easy	80.5%	Bit Manipulation Dynamic Programming	Read
339. Nested List Weight Sum	Medium	85.9%	Breadth-First Search Depth-First Search	Read
340. Longest Substring with At Most K Distinct Characters	Medium	49.9%	Hash Table Sliding Window+1	Read
341. Flatten Nested List Iterator	Medium	65.6%	Depth-First Search Design+4	Read
342. Power of Four	Easy	52.5%	Bit Manipulation Math+1	Read
343. Integer Break	Medium	62.6%	Dynamic Programming Math	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
347. Top K Frequent Elements	Medium	67.3%	Array Bucket Sort+6	Read
348. Design Tic-Tac-Toe	Medium	58.8%	Array Design+3	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

#301Hard

Remove Invalid Parentheses

BacktrackingBreadth-First SearchString

Acceptance: 49.8%

#302Hard

Smallest Rectangle Enclosing Black Pixels

ArrayBinary SearchBreadth-First Search+2

Acceptance: 60.9%

#303Easy

Range Sum Query - Immutable

ArrayDesignPrefix Sum

Acceptance: 73.5%

#304Medium

Range Sum Query 2D - Immutable

ArrayDesignMatrix+1

Acceptance: 58.6%

#305Hard

Number of Islands II

ArrayHash TableUnion Find

Acceptance: 40.5%

#306Medium

Additive Number

BacktrackingString

Acceptance: 34.2%

#307Medium

Range Sum Query - Mutable

ArrayBinary Indexed TreeDesign+1

Acceptance: 43.3%

#308Medium

Range Sum Query 2D - Mutable

ArrayBinary Indexed TreeDesign+2

Acceptance: 46.0%

#309Medium

Best Time to Buy and Sell Stock with Cooldown

ArrayDynamic Programming

Acceptance: 62.4%

#310Medium

Minimum Height Trees

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 42.4%

#311Medium

Sparse Matrix Multiplication

ArrayHash TableMatrix

Acceptance: 69.3%

#312Hard

Burst Balloons

ArrayDynamic Programming

Acceptance: 64.3%

#313Medium

Super Ugly Number

ArrayDynamic ProgrammingMath

Acceptance: 46.6%

#314Medium

Binary Tree Vertical Order Traversal

Binary TreeBreadth-First SearchDepth-First Search+3

Acceptance: 57.8%

#315Hard

Count of Smaller Numbers After Self

ArrayBinary Indexed TreeBinary Search+4

Acceptance: 44.0%

#316Medium

Remove Duplicate Letters

GreedyMonotonic StackStack+1

Acceptance: 54.1%

#317Hard

Shortest Distance from All Buildings

ArrayBreadth-First SearchMatrix

Acceptance: 44.9%

#318Medium

Maximum Product of Word Lengths

ArrayBit ManipulationString

Acceptance: 61.1%

#319Medium

Bulb Switcher

BrainteaserMath

Acceptance: 56.2%

#320Medium

Generalized Abbreviation

BacktrackingBit ManipulationString

Acceptance: 60.4%

#321Hard

Create Maximum Number

ArrayGreedyMonotonic Stack+2

Acceptance: 36.7%

#322Medium

Coin Change

ArrayBreadth-First SearchDynamic Programming

Acceptance: 48.7%

#323Medium

Number of Connected Components in an Undirected Graph

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 64.9%

#324Medium

Wiggle Sort II

ArrayDivide and ConquerGreedy+2

Acceptance: 38.4%

#325Medium

Maximum Size Subarray Sum Equals k

ArrayHash TablePrefix Sum

Acceptance: 50.8%

#326Easy

Power of Three

MathRecursion

Acceptance: 51.4%

#327Hard

Count of Range Sum

ArrayBinary Indexed TreeBinary Search+4

Acceptance: 39.7%

#328Medium

Odd Even Linked List

Linked List

Acceptance: 62.4%

#329Hard

Longest Increasing Path in a Matrix

ArrayBreadth-First SearchDepth-First Search+5

Acceptance: 57.0%

#330Hard

Patching Array

ArrayGreedy

Acceptance: 54.7%

#331Medium

Verify Preorder Serialization of a Binary Tree

Binary TreeStackString+1

Acceptance: 47.8%

#332Hard

Reconstruct Itinerary

Depth-First SearchEulerian CircuitGraph

Acceptance: 45.0%

#333Medium

Largest BST Subtree

Binary Search TreeBinary TreeDepth-First Search+2

Acceptance: 45.8%

#334Medium

Increasing Triplet Subsequence

ArrayGreedy

Acceptance: 39.3%

#335Hard

Self Crossing

ArrayGeometryMath

Acceptance: 36.3%

#336Hard

Palindrome Pairs

ArrayHash TableString+1

Acceptance: 37.1%

#337Medium

House Robber III

Binary TreeDepth-First SearchDynamic Programming+1

Acceptance: 56.3%

#338Easy

Counting Bits

Bit ManipulationDynamic Programming

Acceptance: 80.5%

#339Medium

Nested List Weight Sum

Breadth-First SearchDepth-First Search

Acceptance: 85.9%

#340Medium

Longest Substring with At Most K Distinct Characters

Hash TableSliding WindowString

Acceptance: 49.9%

#341Medium

Flatten Nested List Iterator

Depth-First SearchDesignIterator+3

Acceptance: 65.6%

#342Easy

Power of Four

Bit ManipulationMathRecursion

Acceptance: 52.5%

#343Medium

Integer Break

Dynamic ProgrammingMath

Acceptance: 62.6%

#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%

#347Medium

Top K Frequent Elements

ArrayBucket SortCounting+5

Acceptance: 67.3%

#348Medium

Design Tic-Tac-Toe

ArrayDesignHash Table+2

Acceptance: 58.8%

#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%

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