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
251. Flatten 2D Vector	Medium	50.5%	Array Design+2	Read
252. Meeting Rooms	Easy	59.4%	Array Sorting	Read
253. Meeting Rooms II	Medium	52.6%	Array Greedy+4	Read
254. Factor Combinations	Medium	50.5%	Backtracking	Read
255. Verify Preorder Sequence in Binary Search Tree	Medium	51.7%	Array Binary Search Tree+5	Read
256. Paint House	Medium	64.3%	Array Dynamic Programming	Read
257. Binary Tree Paths	Easy	68.9%	Backtracking Binary Tree+3	Read
258. Add Digits	Easy	69.3%	Math Number Theory+1	Read
259. 3Sum Smaller	Medium	51.4%	Array Binary Search+2	Read
260. Single Number III	Medium	70.2%	Array Bit Manipulation	Read
261. Graph Valid Tree	Medium	49.9%	Breadth-First Search Depth-First Search+2	Read
262. Trips and Users	Hard	36.7%	Database	Read
263. Ugly Number	Easy	43.9%	Math	Read
264. Ugly Number II	Medium	49.7%	Dynamic Programming Hash Table+2	Read
265. Paint House II	Hard	57.0%	Array Dynamic Programming	Read
266. Palindrome Permutation	Easy	68.6%	Bit Manipulation Hash Table+1	Read
267. Palindrome Permutation II	Medium	41.9%	Backtracking Hash Table+1	Read
268. Missing Number	Easy	72.4%	Array Binary Search+4	Read
269. Alien Dictionary	Hard	37.1%	Array Breadth-First Search+4	Read
270. Closest Binary Search Tree Value	Easy	49.2%	Binary Search Binary Search Tree+3	Read
271. Encode and Decode Strings	Medium	51.9%	Array Design+1	Read
272. Closest Binary Search Tree Value II	Hard	61.1%	Binary Search Tree Binary Tree+5	Read
273. Integer to English Words	Hard	34.9%	Math Recursion+1	Read
274. H-Index	Medium	41.8%	Array Counting Sort+1	Read
275. H-Index II	Medium	40.0%	Array Binary Search	Read
276. Paint Fence	Medium	48.3%	Dynamic Programming	Read
277. Find the Celebrity	Medium	48.9%	Graph Interactive+1	Read
278. First Bad Version	Easy	47.5%	Binary Search Interactive	Read
279. Perfect Squares	Medium	56.4%	Breadth-First Search Dynamic Programming+1	Read
280. Wiggle Sort	Medium	68.5%	Array Greedy+1	Read
281. Zigzag Iterator	Medium	67.1%	Array Design+2	Read
282. Expression Add Operators	Hard	43.5%	Backtracking Math+1	Read
283. Move Zeroes	Easy	64.3%	Array Two Pointers	Read
284. Peeking Iterator	Medium	61.9%	Array Design+1	Read
285. Inorder Successor in BST	Medium	51.2%	Binary Search Tree Binary Tree+2	Read
286. Walls and Gates	Medium	63.9%	Array Breadth-First Search+1	Read
287. Find the Duplicate Number	Medium	64.7%	Array Binary Search+2	Read
288. Unique Word Abbreviation	Medium	27.5%	Array Design+2	Read
289. Game of Life	Medium	73.0%	Array Matrix+1	Read
290. Word Pattern	Easy	44.5%	Hash Table String	Read
291. Word Pattern II	Medium	49.1%	Backtracking Hash Table+1	Read
292. Nim Game	Easy	60.0%	Brainteaser Game Theory+1	Read
293. Flip Game	Easy	64.8%	String	Read
294. Flip Game II	Medium	52.2%	Backtracking Dynamic Programming+3	Read
295. Find Median from Data Stream	Hard	54.9%	Data Stream Design+3	Read
296. Best Meeting Point	Hard	61.1%	Array Math+2	Read
297. Serialize and Deserialize Binary Tree	Hard	61.1%	Binary Tree Breadth-First Search+4	Read
298. Binary Tree Longest Consecutive Sequence	Medium	54.7%	Binary Tree Depth-First Search+1	Read
299. Bulls and Cows	Medium	52.9%	Counting Hash Table+1	Read
300. Longest Increasing Subsequence	Medium	59.8%	Array Binary Search+1	Read

#251Medium

Flatten 2D Vector

ArrayDesignIterator+1

Acceptance: 50.5%

#252Easy

Meeting Rooms

ArraySorting

Acceptance: 59.4%

#253Medium

Meeting Rooms II

ArrayGreedyHeap (Priority Queue)+3

Acceptance: 52.6%

#254Medium

Factor Combinations

Backtracking

Acceptance: 50.5%

#255Medium

Verify Preorder Sequence in Binary Search Tree

ArrayBinary Search TreeBinary Tree+4

Acceptance: 51.7%

#256Medium

Paint House

ArrayDynamic Programming

Acceptance: 64.3%

#257Easy

Binary Tree Paths

BacktrackingBinary TreeDepth-First Search+2

Acceptance: 68.9%

#258Easy

Add Digits

MathNumber TheorySimulation

Acceptance: 69.3%

#259Medium

3Sum Smaller

ArrayBinary SearchSorting+1

Acceptance: 51.4%

#260Medium

Single Number III

ArrayBit Manipulation

Acceptance: 70.2%

#261Medium

Graph Valid Tree

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 49.9%

#262Hard

Trips and Users

Database

Acceptance: 36.7%

#263Easy

Ugly Number

Math

Acceptance: 43.9%

#264Medium

Ugly Number II

Dynamic ProgrammingHash TableHeap (Priority Queue)+1

Acceptance: 49.7%

#265Hard

Paint House II

ArrayDynamic Programming

Acceptance: 57.0%

#266Easy

Palindrome Permutation

Bit ManipulationHash TableString

Acceptance: 68.6%

#267Medium

Palindrome Permutation II

BacktrackingHash TableString

Acceptance: 41.9%

#268Easy

Missing Number

ArrayBinary SearchBit Manipulation+3

Acceptance: 72.4%

#269Hard

Alien Dictionary

ArrayBreadth-First SearchDepth-First Search+3

Acceptance: 37.1%

#270Easy

Closest Binary Search Tree Value

Binary SearchBinary Search TreeBinary Tree+2

Acceptance: 49.2%

#271Medium

Encode and Decode Strings

ArrayDesignString

Acceptance: 51.9%

#272Hard

Closest Binary Search Tree Value II

Binary Search TreeBinary TreeDepth-First Search+4

Acceptance: 61.1%

#273Hard

Integer to English Words

MathRecursionString

Acceptance: 34.9%

#274Medium

H-Index

ArrayCounting SortSorting

Acceptance: 41.8%

#275Medium

H-Index II

ArrayBinary Search

Acceptance: 40.0%

#276Medium

Paint Fence

Dynamic Programming

Acceptance: 48.3%

#277Medium

Find the Celebrity

GraphInteractiveTwo Pointers

Acceptance: 48.9%

#278Easy

First Bad Version

Binary SearchInteractive

Acceptance: 47.5%

#279Medium

Perfect Squares

Breadth-First SearchDynamic ProgrammingMath

Acceptance: 56.4%

#280Medium

Wiggle Sort

ArrayGreedySorting

Acceptance: 68.5%

#281Medium

Zigzag Iterator

ArrayDesignIterator+1

Acceptance: 67.1%

#282Hard

Expression Add Operators

BacktrackingMathString

Acceptance: 43.5%

#283Easy

Move Zeroes

ArrayTwo Pointers

Acceptance: 64.3%

#284Medium

Peeking Iterator

ArrayDesignIterator

Acceptance: 61.9%

#285Medium

Inorder Successor in BST

Binary Search TreeBinary TreeDepth-First Search+1

Acceptance: 51.2%

#286Medium

Walls and Gates

ArrayBreadth-First SearchMatrix

Acceptance: 63.9%

#287Medium

Find the Duplicate Number

ArrayBinary SearchBit Manipulation+1

Acceptance: 64.7%

#288Medium

Unique Word Abbreviation

ArrayDesignHash Table+1

Acceptance: 27.5%

#289Medium

Game of Life

ArrayMatrixSimulation

Acceptance: 73.0%

#290Easy

Word Pattern

Hash TableString

Acceptance: 44.5%

#291Medium

Word Pattern II

BacktrackingHash TableString

Acceptance: 49.1%

#292Easy

Nim Game

BrainteaserGame TheoryMath

Acceptance: 60.0%

#293Easy

Flip Game

String

Acceptance: 64.8%

#294Medium

Flip Game II

BacktrackingDynamic ProgrammingGame Theory+2

Acceptance: 52.2%

#295Hard

Find Median from Data Stream

Data StreamDesignHeap (Priority Queue)+2

Acceptance: 54.9%

#296Hard

Best Meeting Point

ArrayMathMatrix+1

Acceptance: 61.1%

#297Hard

Serialize and Deserialize Binary Tree

Binary TreeBreadth-First SearchDepth-First Search+3

Acceptance: 61.1%

#298Medium

Binary Tree Longest Consecutive Sequence

Binary TreeDepth-First SearchTree

Acceptance: 54.7%

#299Medium

Bulls and Cows

CountingHash TableString

Acceptance: 52.9%

#300Medium

Longest Increasing Subsequence

ArrayBinary SearchDynamic Programming

Acceptance: 59.8%

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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