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
305. Number of Islands II	Hard	40.5%	Array Hash Table+1	Read
312. Burst Balloons	Hard	64.3%	Array Dynamic Programming	Read
315. Count of Smaller Numbers After Self	Hard	44.0%	Array Binary Indexed Tree+5	Read
317. Shortest Distance from All Buildings	Hard	44.9%	Array Breadth-First Search+1	Read
321. Create Maximum Number	Hard	36.7%	Array Greedy+3	Read
327. Count of Range Sum	Hard	39.7%	Array Binary Indexed Tree+5	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
332. Reconstruct Itinerary	Hard	45.0%	Depth-First Search Eulerian Circuit+1	Read
335. Self Crossing	Hard	36.3%	Array Geometry+1	Read
336. Palindrome Pairs	Hard	37.1%	Array Hash Table+2	Read
352. Data Stream as Disjoint Intervals	Hard	60.2%	Binary Search Design+1	Read
354. Russian Doll Envelopes	Hard	37.8%	Array Binary Search+2	Read
358. Rearrange String k Distance Apart	Hard	39.9%	Counting Greedy+4	Read
363. Max Sum of Rectangle No Larger Than K	Hard	46.0%	Array Binary Search+3	Read
381. Insert Delete GetRandom O(1) - Duplicates allowed	Hard	36.5%	Array Design+3	Read
391. Perfect Rectangle	Hard	38.8%	Array Line Sweep	Read
403. Frog Jump	Hard	47.2%	Array Dynamic Programming	Read
407. Trapping Rain Water II	Hard	64.0%	Array Breadth-First Search+2	Read
410. Split Array Largest Sum	Hard	61.2%	Array Binary Search+3	Read
411. Minimum Unique Word Abbreviation	Hard	40.5%	Array Backtracking+2	Read
420. Strong Password Checker	Hard	16.1%	Greedy Heap (Priority Queue)+1	Read
425. Word Squares	Hard	54.7%	Array Backtracking+2	Read
428. Serialize and Deserialize N-ary Tree	Hard	68.7%	Breadth-First Search Depth-First Search+2	Read
431. Encode N-ary Tree to Binary Tree	Hard	80.6%	Binary Tree Breadth-First Search+3	Read
432. All O`one Data Structure	Hard	44.2%	Design Doubly-Linked List+2	Read
440. K-th Smallest in Lexicographical Order	Hard	46.2%	Trie	Read
446. Arithmetic Slices II - Subsequence	Hard	55.1%	Array Dynamic Programming	Read
458. Poor Pigs	Hard	59.4%	Combinatorics Dynamic Programming+1	Read
460. LFU Cache	Hard	50.0%	Design Doubly-Linked List+2	Read
465. Optimal Account Balancing	Hard	50.3%	Array Backtracking+3	Read
466. Count The Repetitions	Hard	36.0%	Dynamic Programming String	Read
471. Encode String with Shortest Length	Hard	50.5%	Dynamic Programming String	Read
472. Concatenated Words	Hard	49.9%	Array Depth-First Search+3	Read
479. Largest Palindrome Product	Hard	39.6%	Enumeration Math	Read
480. Sliding Window Median	Hard	38.7%	Array Hash Table+2	Read
483. Smallest Good Base	Hard	47.0%	Binary Search Math	Read
488. Zuma Game	Hard	29.4%	Breadth-First Search Dynamic Programming+3	Read
489. Robot Room Cleaner	Hard	77.9%	Backtracking Interactive	Read
493. Reverse Pairs	Hard	35.1%	Array Binary Indexed Tree+5	Read
499. The Maze III	Hard	52.3%	Array Breadth-First Search+6	Read
502. IPO	Hard	53.6%	Array Greedy+2	Read
514. Freedom Trail	Hard	59.4%	Breadth-First Search Depth-First Search+2	Read
517. Super Washing Machines	Hard	45.3%	Array Greedy	Read
527. Word Abbreviation	Hard	62.7%	Array Greedy+3	Read
546. Remove Boxes	Hard	49.4%	Array Dynamic Programming+1	Read
548. Split Array with Equal Sum	Hard	50.1%	Array Hash Table+1	Read
552. Student Attendance Record II	Hard	56.5%	Dynamic Programming	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%

#305Hard

Number of Islands II

ArrayHash TableUnion Find

Acceptance: 40.5%

#312Hard

Burst Balloons

ArrayDynamic Programming

Acceptance: 64.3%

#315Hard

Count of Smaller Numbers After Self

ArrayBinary Indexed TreeBinary Search+4

Acceptance: 44.0%

#317Hard

Shortest Distance from All Buildings

ArrayBreadth-First SearchMatrix

Acceptance: 44.9%

#321Hard

Create Maximum Number

ArrayGreedyMonotonic Stack+2

Acceptance: 36.7%

#327Hard

Count of Range Sum

ArrayBinary Indexed TreeBinary Search+4

Acceptance: 39.7%

#329Hard

Longest Increasing Path in a Matrix

ArrayBreadth-First SearchDepth-First Search+5

Acceptance: 57.0%

#330Hard

Patching Array

ArrayGreedy

Acceptance: 54.7%

#332Hard

Reconstruct Itinerary

Depth-First SearchEulerian CircuitGraph

Acceptance: 45.0%

#335Hard

Self Crossing

ArrayGeometryMath

Acceptance: 36.3%

#336Hard

Palindrome Pairs

ArrayHash TableString+1

Acceptance: 37.1%

#352Hard

Data Stream as Disjoint Intervals

Binary SearchDesignOrdered Set

Acceptance: 60.2%

#354Hard

Russian Doll Envelopes

ArrayBinary SearchDynamic Programming+1

Acceptance: 37.8%

#358Hard

Rearrange String k Distance Apart

CountingGreedyHash Table+3

Acceptance: 39.9%

#363Hard

Max Sum of Rectangle No Larger Than K

ArrayBinary SearchMatrix+2

Acceptance: 46.0%

#381Hard

Insert Delete GetRandom O(1) - Duplicates allowed

ArrayDesignHash Table+2

Acceptance: 36.5%

#391Hard

Perfect Rectangle

ArrayLine Sweep

Acceptance: 38.8%

#403Hard

Frog Jump

ArrayDynamic Programming

Acceptance: 47.2%

#407Hard

Trapping Rain Water II

ArrayBreadth-First SearchHeap (Priority Queue)+1

Acceptance: 64.0%

#410Hard

Split Array Largest Sum

ArrayBinary SearchDynamic Programming+2

Acceptance: 61.2%

#411Hard

Minimum Unique Word Abbreviation

ArrayBacktrackingBit Manipulation+1

Acceptance: 40.5%

#420Hard

Strong Password Checker

GreedyHeap (Priority Queue)String

Acceptance: 16.1%

#425Hard

Word Squares

ArrayBacktrackingString+1

Acceptance: 54.7%

#428Hard

Serialize and Deserialize N-ary Tree

Breadth-First SearchDepth-First SearchString+1

Acceptance: 68.7%

#431Hard

Encode N-ary Tree to Binary Tree

Binary TreeBreadth-First SearchDepth-First Search+2

Acceptance: 80.6%

#432Hard

All O`one Data Structure

DesignDoubly-Linked ListHash Table+1

Acceptance: 44.2%

#440Hard

K-th Smallest in Lexicographical Order

Trie

Acceptance: 46.2%

#446Hard

Arithmetic Slices II - Subsequence

ArrayDynamic Programming

Acceptance: 55.1%

#458Hard

Poor Pigs

CombinatoricsDynamic ProgrammingMath

Acceptance: 59.4%

#460Hard

LFU Cache

DesignDoubly-Linked ListHash Table+1

Acceptance: 50.0%

#465Hard

Optimal Account Balancing

ArrayBacktrackingBit Manipulation+2

Acceptance: 50.3%

#466Hard

Count The Repetitions

Dynamic ProgrammingString

Acceptance: 36.0%

#471Hard

Encode String with Shortest Length

Dynamic ProgrammingString

Acceptance: 50.5%

#472Hard

Concatenated Words

ArrayDepth-First SearchDynamic Programming+2

Acceptance: 49.9%

#479Hard

Largest Palindrome Product

EnumerationMath

Acceptance: 39.6%

#480Hard

Sliding Window Median

ArrayHash TableHeap (Priority Queue)+1

Acceptance: 38.7%

#483Hard

Smallest Good Base

Binary SearchMath

Acceptance: 47.0%

#488Hard

Zuma Game

Breadth-First SearchDynamic ProgrammingMemoization+2

Acceptance: 29.4%

#489Hard

Robot Room Cleaner

BacktrackingInteractive

Acceptance: 77.9%

#493Hard

Reverse Pairs

ArrayBinary Indexed TreeBinary Search+4

Acceptance: 35.1%

#499Hard

The Maze III

ArrayBreadth-First SearchDepth-First Search+5

Acceptance: 52.3%

#502Hard

IPO

ArrayGreedyHeap (Priority Queue)+1

Acceptance: 53.6%

#514Hard

Freedom Trail

Breadth-First SearchDepth-First SearchDynamic Programming+1

Acceptance: 59.4%

#517Hard

Super Washing Machines

ArrayGreedy

Acceptance: 45.3%

#527Hard

Word Abbreviation

ArrayGreedySorting+2

Acceptance: 62.7%

#546Hard

Remove Boxes

ArrayDynamic ProgrammingMemoization

Acceptance: 49.4%

#548Hard

Split Array with Equal Sum

ArrayHash TablePrefix Sum

Acceptance: 50.1%

#552Hard

Student Attendance Record II

Dynamic Programming

Acceptance: 56.5%

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