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
348. Design Tic-Tac-Toe	Medium	58.8%	Array Design+3	Read
351. Android Unlock Patterns	Medium	53.8%	Backtracking Bit Manipulation+2	Read
353. Design Snake Game	Medium	40.0%	Array Design+3	Read
355. Design Twitter	Medium	45.6%	Design Hash Table+2	Read
356. Line Reflection	Medium	36.3%	Array Hash Table+1	Read
357. Count Numbers with Unique Digits	Medium	56.1%	Backtracking Dynamic Programming+1	Read
360. Sort Transformed Array	Medium	58.0%	Array Math+2	Read
361. Bomb Enemy	Medium	52.8%	Array Dynamic Programming+1	Read
362. Design Hit Counter	Medium	69.6%	Array Binary Search+3	Read
364. Nested List Weight Sum II	Medium	66.8%	Breadth-First Search Depth-First Search+1	Read
365. Water and Jug Problem	Medium	46.4%	Breadth-First Search Depth-First Search+1	Read
366. Find Leaves of Binary Tree	Medium	81.4%	Binary Tree Depth-First Search+1	Read
368. Largest Divisible Subset	Medium	50.1%	Array Dynamic Programming+2	Read
369. Plus One Linked List	Medium	61.1%	Linked List Math	Read
370. Range Addition	Medium	73.0%	Array Prefix Sum	Read
371. Sum of Two Integers	Medium	55.9%	Bit Manipulation Math	Read
372. Super Pow	Medium	37.3%	Divide and Conquer Math	Read
373. Find K Pairs with Smallest Sums	Medium	42.3%	Array Heap (Priority Queue)	Read
375. Guess Number Higher or Lower II	Medium	53.2%	Dynamic Programming Game Theory+1	Read
376. Wiggle Subsequence	Medium	49.3%	Array Dynamic Programming+1	Read
377. Combination Sum IV	Medium	55.0%	Array Dynamic Programming	Read
378. Kth Smallest Element in a Sorted Matrix	Medium	65.1%	Array Binary Search+3	Read
379. Design Phone Directory	Medium	52.7%	Array Design+3	Read
380. Insert Delete GetRandom O(1)	Medium	55.3%	Array Design+3	Read
382. Linked List Random Node	Medium	64.7%	Linked List Math+2	Read
384. Shuffle an Array	Medium	59.6%	Array Design+2	Read
385. Mini Parser	Medium	43.4%	Depth-First Search Stack+1	Read
386. Lexicographical Numbers	Medium	76.2%	Depth-First Search Trie	Read
388. Longest Absolute File Path	Medium	49.9%	Depth-First Search Stack+1	Read
390. Elimination Game	Medium	46.7%	Math Recursion	Read
393. UTF-8 Validation	Medium	46.7%	Array Bit Manipulation	Read
394. Decode String	Medium	63.0%	Recursion Stack+1	Read
395. Longest Substring with At Least K Repeating Characters	Medium	46.2%	Divide and Conquer Hash Table+2	Read
396. Rotate Function	Medium	54.0%	Array Dynamic Programming+1	Read
397. Integer Replacement	Medium	37.9%	Bit Manipulation Dynamic Programming+2	Read
398. Random Pick Index	Medium	65.0%	Hash Table Math+2	Read
399. Evaluate Division	Medium	64.1%	Array Breadth-First Search+5	Read
400. Nth Digit	Medium	38.8%	Binary Search Math	Read
402. Remove K Digits	Medium	37.7%	Greedy Monotonic Stack+2	Read
406. Queue Reconstruction by Height	Medium	74.6%	Array Binary Indexed Tree+2	Read
413. Arithmetic Slices	Medium	65.0%	Array Dynamic Programming+1	Read
416. Partition Equal Subset Sum	Medium	49.9%	Array Dynamic Programming	Read
417. Pacific Atlantic Water Flow	Medium	61.3%	Array Breadth-First Search+2	Read
418. Sentence Screen Fitting	Medium	36.3%	Array Dynamic Programming+1	Read
419. Battleships in a Board	Medium	77.4%	Array Depth-First Search+1	Read
421. Maximum XOR of Two Numbers in an Array	Medium	53.8%	Array Bit Manipulation+2	Read
423. Reconstruct Original Digits from English	Medium	52.8%	Hash Table Math+1	Read
424. Longest Repeating Character Replacement	Medium	60.4%	Hash Table Sliding Window+1	Read
426. Convert Binary Search Tree to Sorted Doubly Linked List	Medium	65.2%	Binary Search Tree Binary Tree+5	Read
427. Construct Quad Tree	Medium	78.2%	Array Divide and Conquer+2	Read

#348Medium

Design Tic-Tac-Toe

ArrayDesignHash Table+2

Acceptance: 58.8%

#351Medium

Android Unlock Patterns

BacktrackingBit ManipulationBitmask+1

Acceptance: 53.8%

#353Medium

Design Snake Game

ArrayDesignHash Table+2

Acceptance: 40.0%

#355Medium

Design Twitter

DesignHash TableHeap (Priority Queue)+1

Acceptance: 45.6%

#356Medium

Line Reflection

ArrayHash TableMath

Acceptance: 36.3%

#357Medium

Count Numbers with Unique Digits

BacktrackingDynamic ProgrammingMath

Acceptance: 56.1%

#360Medium

Sort Transformed Array

ArrayMathSorting+1

Acceptance: 58.0%

#361Medium

Bomb Enemy

ArrayDynamic ProgrammingMatrix

Acceptance: 52.8%

#362Medium

Design Hit Counter

ArrayBinary SearchData Stream+2

Acceptance: 69.6%

#364Medium

Nested List Weight Sum II

Breadth-First SearchDepth-First SearchStack

Acceptance: 66.8%

#365Medium

Water and Jug Problem

Breadth-First SearchDepth-First SearchMath

Acceptance: 46.4%

#366Medium

Find Leaves of Binary Tree

Binary TreeDepth-First SearchTree

Acceptance: 81.4%

#368Medium

Largest Divisible Subset

ArrayDynamic ProgrammingMath+1

Acceptance: 50.1%

#369Medium

Plus One Linked List

Linked ListMath

Acceptance: 61.1%

#370Medium

Range Addition

ArrayPrefix Sum

Acceptance: 73.0%

#371Medium

Sum of Two Integers

Bit ManipulationMath

Acceptance: 55.9%

#372Medium

Super Pow

Divide and ConquerMath

Acceptance: 37.3%

#373Medium

Find K Pairs with Smallest Sums

ArrayHeap (Priority Queue)

Acceptance: 42.3%

#375Medium

Guess Number Higher or Lower II

Dynamic ProgrammingGame TheoryMath

Acceptance: 53.2%

#376Medium

Wiggle Subsequence

ArrayDynamic ProgrammingGreedy

Acceptance: 49.3%

#377Medium

Combination Sum IV

ArrayDynamic Programming

Acceptance: 55.0%

#378Medium

Kth Smallest Element in a Sorted Matrix

ArrayBinary SearchHeap (Priority Queue)+2

Acceptance: 65.1%

#379Medium

Design Phone Directory

ArrayDesignHash Table+2

Acceptance: 52.7%

#380Medium

Insert Delete GetRandom O(1)

ArrayDesignHash Table+2

Acceptance: 55.3%

#382Medium

Linked List Random Node

Linked ListMathRandomized+1

Acceptance: 64.7%

#384Medium

Shuffle an Array

ArrayDesignMath+1

Acceptance: 59.6%

#385Medium

Mini Parser

Depth-First SearchStackString

Acceptance: 43.4%

#386Medium

Lexicographical Numbers

Depth-First SearchTrie

Acceptance: 76.2%

#388Medium

Longest Absolute File Path

Depth-First SearchStackString

Acceptance: 49.9%

#390Medium

Elimination Game

MathRecursion

Acceptance: 46.7%

#393Medium

UTF-8 Validation

ArrayBit Manipulation

Acceptance: 46.7%

#394Medium

Decode String

RecursionStackString

Acceptance: 63.0%

#395Medium

Longest Substring with At Least K Repeating Characters

Divide and ConquerHash TableSliding Window+1

Acceptance: 46.2%

#396Medium

Rotate Function

ArrayDynamic ProgrammingMath

Acceptance: 54.0%

#397Medium

Integer Replacement

Bit ManipulationDynamic ProgrammingGreedy+1

Acceptance: 37.9%

#398Medium

Random Pick Index

Hash TableMathRandomized+1

Acceptance: 65.0%

#399Medium

Evaluate Division

ArrayBreadth-First SearchDepth-First Search+4

Acceptance: 64.1%

#400Medium

Nth Digit

Binary SearchMath

Acceptance: 38.8%

#402Medium

Remove K Digits

GreedyMonotonic StackStack+1

Acceptance: 37.7%

#406Medium

Queue Reconstruction by Height

ArrayBinary Indexed TreeSegment Tree+1

Acceptance: 74.6%

#413Medium

Arithmetic Slices

ArrayDynamic ProgrammingSliding Window

Acceptance: 65.0%

#416Medium

Partition Equal Subset Sum

ArrayDynamic Programming

Acceptance: 49.9%

#417Medium

Pacific Atlantic Water Flow

ArrayBreadth-First SearchDepth-First Search+1

Acceptance: 61.3%

#418Medium

Sentence Screen Fitting

ArrayDynamic ProgrammingString

Acceptance: 36.3%

#419Medium

Battleships in a Board

ArrayDepth-First SearchMatrix

Acceptance: 77.4%

#421Medium

Maximum XOR of Two Numbers in an Array

ArrayBit ManipulationHash Table+1

Acceptance: 53.8%

#423Medium

Reconstruct Original Digits from English

Hash TableMathString

Acceptance: 52.8%

#424Medium

Longest Repeating Character Replacement

Hash TableSliding WindowString

Acceptance: 60.4%

#426Medium

Convert Binary Search Tree to Sorted Doubly Linked List

Binary Search TreeBinary TreeDepth-First Search+4

Acceptance: 65.2%

#427Medium

Construct Quad Tree

ArrayDivide and ConquerMatrix+1

Acceptance: 78.2%

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Master DSA with Step-by-Step Solutions

Each solution article on FleetCode breaks down the problem into multiple approaches, from brute force to optimal, with detailed explanations and code in Python, Java, C++ and more. Understanding why an approach works - not just copying code - is what separates candidates who clear interviews from those who don't.

How to Use These Solutions

Try the problem first: Spend at least 20 minutes before reading the solution
Read all approaches: Start from brute force to understand the problem fully, then study the optimized solution
Understand the complexity: Pay attention to time and space analysis for each approach
Code it yourself: After understanding the approach, close the solution and implement from memory
Revisit after a week: Spaced repetition helps retain problem-solving patterns