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
1167. Minimum Cost to Connect Sticks	Medium	71.8%	Array Greedy+1	Read
1169. Invalid Transactions	Medium	32.1%	Array Hash Table+2	Read
1170. Compare Strings by Frequency of the Smallest Character	Medium	63.3%	Array Binary Search+3	Read
1171. Remove Zero Sum Consecutive Nodes from Linked List	Medium	53.3%	Hash Table Linked List	Read
1174. Immediate Food Delivery II	Medium	53.1%	Database	Read
1177. Can Make Palindrome from Substring	Medium	42.0%	Array Bit Manipulation+3	Read
1181. Before and After Puzzle	Medium	51.8%	Array Hash Table+2	Read
1182. Shortest Distance to Target Color	Medium	56.5%	Array Binary Search+1	Read
1186. Maximum Subarray Sum with One Deletion	Medium	49.4%	Array Dynamic Programming	Read
1188. Design Bounded Blocking Queue	Medium	72.6%	Concurrency	Read
1190. Reverse Substrings Between Each Pair of Parentheses	Medium	71.8%	Stack String	Read
1191. K-Concatenation Maximum Sum	Medium	25.9%	Array Dynamic Programming	Read
1193. Monthly Transactions I	Medium	58.3%	Database	Read
1195. Fizz Buzz Multithreaded	Medium	73.2%	Concurrency	Read
1197. Minimum Knight Moves	Medium	41.8%	Breadth-First Search	Read
1198. Find Smallest Common Element in All Rows	Medium	76.5%	Array Binary Search+3	Read
1201. Ugly Number III	Medium	31.9%	Binary Search Combinatorics+2	Read
1202. Smallest String With Swaps	Medium	61.0%	Array Breadth-First Search+5	Read
1204. Last Person to Fit in the Bus	Medium	68.0%	Database	Read
1205. Monthly Transactions II	Medium	41.8%	Database	Read
1208. Get Equal Substrings Within Budget	Medium	60.2%	Binary Search Prefix Sum+2	Read
1209. Remove All Adjacent Duplicates in String II	Medium	61.7%	Stack String	Read
1212. Team Scores in Football Tournament	Medium	55.6%	Database	Read
1214. Two Sum BSTs	Medium	68.2%	Binary Search Binary Search Tree+5	Read
1215. Stepping Numbers	Medium	48.2%	Backtracking Breadth-First Search+1	Read
1218. Longest Arithmetic Subsequence of Given Difference	Medium	54.5%	Array Dynamic Programming+1	Read
1219. Path with Maximum Gold	Medium	68.6%	Array Backtracking+1	Read
1222. Queens That Can Attack the King	Medium	72.6%	Array Matrix+1	Read
1226. The Dining Philosophers	Medium	54.5%	Concurrency	Read
1227. Airplane Seat Assignment Probability	Medium	67.3%	Brainteaser Dynamic Programming+2	Read
1229. Meeting Scheduler	Medium	55.3%	Array Sorting+1	Read
1230. Toss Strange Coins	Medium	58.1%	Array Dynamic Programming+2	Read
1233. Remove Sub-Folders from the Filesystem	Medium	78.6%	Array Depth-First Search+2	Read
1234. Replace the Substring for Balanced String	Medium	41.3%	Sliding Window String	Read
1236. Web Crawler	Medium	68.8%	Breadth-First Search Depth-First Search+2	Read
1237. Find Positive Integer Solution for a Given Equation	Medium	69.7%	Binary Search Interactive+2	Read
1238. Circular Permutation in Binary Representation	Medium	72.6%	Backtracking Bit Manipulation+1	Read
1239. Maximum Length of a Concatenated String with Unique Characters	Medium	54.7%	Array Backtracking+2	Read
1242. Web Crawler Multithreaded	Medium	49.5%	Breadth-First Search Concurrency+1	Read
1244. Design A Leaderboard	Medium	67.9%	Design Hash Table+1	Read
1245. Tree Diameter	Medium	61.1%	Breadth-First Search Depth-First Search+3	Read
1247. Minimum Swaps to Make Strings Equal	Medium	65.3%	Greedy Math+1	Read
1248. Count Number of Nice Subarrays	Medium	75.5%	Array Hash Table+3	Read
1249. Minimum Remove to Make Valid Parentheses	Medium	71.3%	Stack String	Read
1253. Reconstruct a 2-Row Binary Matrix	Medium	49.4%	Array Greedy+1	Read
1254. Number of Closed Islands	Medium	67.1%	Array Breadth-First Search+3	Read
1256. Encode Number	Medium	70.0%	Bit Manipulation Math+1	Read
1257. Smallest Common Region	Medium	68.6%	Array Breadth-First Search+4	Read
1258. Synonymous Sentences	Medium	57.2%	Array Backtracking+3	Read
1261. Find Elements in a Contaminated Binary Tree	Medium	84.1%	Binary Tree Breadth-First Search+4	Read

#1167Medium

Minimum Cost to Connect Sticks

ArrayGreedyHeap (Priority Queue)

Acceptance: 71.8%

#1169Medium

Invalid Transactions

ArrayHash TableSorting+1

Acceptance: 32.1%

#1170Medium

Compare Strings by Frequency of the Smallest Character

ArrayBinary SearchHash Table+2

Acceptance: 63.3%

#1171Medium

Remove Zero Sum Consecutive Nodes from Linked List

Hash TableLinked List

Acceptance: 53.3%

#1174Medium

Immediate Food Delivery II

Database

Acceptance: 53.1%

#1177Medium

Can Make Palindrome from Substring

ArrayBit ManipulationHash Table+2

Acceptance: 42.0%

#1181Medium

Before and After Puzzle

ArrayHash TableSorting+1

Acceptance: 51.8%

#1182Medium

Shortest Distance to Target Color

ArrayBinary SearchDynamic Programming

Acceptance: 56.5%

#1186Medium

Maximum Subarray Sum with One Deletion

ArrayDynamic Programming

Acceptance: 49.4%

#1188Medium

Design Bounded Blocking Queue

Concurrency

Acceptance: 72.6%

#1190Medium

Reverse Substrings Between Each Pair of Parentheses

StackString

Acceptance: 71.8%

#1191Medium

K-Concatenation Maximum Sum

ArrayDynamic Programming

Acceptance: 25.9%

#1193Medium

Monthly Transactions I

Database

Acceptance: 58.3%

#1195Medium

Fizz Buzz Multithreaded

Concurrency

Acceptance: 73.2%

#1197Medium

Minimum Knight Moves

Breadth-First Search

Acceptance: 41.8%

#1198Medium

Find Smallest Common Element in All Rows

ArrayBinary SearchCounting+2

Acceptance: 76.5%

#1201Medium

Ugly Number III

Binary SearchCombinatoricsMath+1

Acceptance: 31.9%

#1202Medium

Smallest String With Swaps

ArrayBreadth-First SearchDepth-First Search+4

Acceptance: 61.0%

#1204Medium

Last Person to Fit in the Bus

Database

Acceptance: 68.0%

#1205Medium

Monthly Transactions II

Database

Acceptance: 41.8%

#1208Medium

Get Equal Substrings Within Budget

Binary SearchPrefix SumSliding Window+1

Acceptance: 60.2%

#1209Medium

Remove All Adjacent Duplicates in String II

StackString

Acceptance: 61.7%

#1212Medium

Team Scores in Football Tournament

Database

Acceptance: 55.6%

#1214Medium

Two Sum BSTs

Binary SearchBinary Search TreeBinary Tree+4

Acceptance: 68.2%

#1215Medium

Stepping Numbers

BacktrackingBreadth-First SearchMath

Acceptance: 48.2%

#1218Medium

Longest Arithmetic Subsequence of Given Difference

ArrayDynamic ProgrammingHash Table

Acceptance: 54.5%

#1219Medium

Path with Maximum Gold

ArrayBacktrackingMatrix

Acceptance: 68.6%

#1222Medium

Queens That Can Attack the King

ArrayMatrixSimulation

Acceptance: 72.6%

#1226Medium

The Dining Philosophers

Concurrency

Acceptance: 54.5%

#1227Medium

Airplane Seat Assignment Probability

BrainteaserDynamic ProgrammingMath+1

Acceptance: 67.3%

#1229Medium

Meeting Scheduler

ArraySortingTwo Pointers

Acceptance: 55.3%

#1230Medium

Toss Strange Coins

ArrayDynamic ProgrammingMath+1

Acceptance: 58.1%

#1233Medium

Remove Sub-Folders from the Filesystem

ArrayDepth-First SearchString+1

Acceptance: 78.6%

#1234Medium

Replace the Substring for Balanced String

Sliding WindowString

Acceptance: 41.3%

#1236Medium

Web Crawler

Breadth-First SearchDepth-First SearchInteractive+1

Acceptance: 68.8%

#1237Medium

Find Positive Integer Solution for a Given Equation

Binary SearchInteractiveMath+1

Acceptance: 69.7%

#1238Medium

Circular Permutation in Binary Representation

BacktrackingBit ManipulationMath

Acceptance: 72.6%

#1239Medium

Maximum Length of a Concatenated String with Unique Characters

ArrayBacktrackingBit Manipulation+1

Acceptance: 54.7%

#1242Medium

Web Crawler Multithreaded

Breadth-First SearchConcurrencyDepth-First Search

Acceptance: 49.5%

#1244Medium

Design A Leaderboard

DesignHash TableSorting

Acceptance: 67.9%

#1245Medium

Tree Diameter

Breadth-First SearchDepth-First SearchGraph+2

Acceptance: 61.1%

#1247Medium

Minimum Swaps to Make Strings Equal

GreedyMathString

Acceptance: 65.3%

#1248Medium

Count Number of Nice Subarrays

ArrayHash TableMath+2

Acceptance: 75.5%

#1249Medium

Minimum Remove to Make Valid Parentheses

StackString

Acceptance: 71.3%

#1253Medium

Reconstruct a 2-Row Binary Matrix

ArrayGreedyMatrix

Acceptance: 49.4%

#1254Medium

Number of Closed Islands

ArrayBreadth-First SearchDepth-First Search+2

Acceptance: 67.1%

#1256Medium

Encode Number

Bit ManipulationMathString

Acceptance: 70.0%

#1257Medium

Smallest Common Region

ArrayBreadth-First SearchDepth-First Search+3

Acceptance: 68.6%

#1258Medium

Synonymous Sentences

ArrayBacktrackingHash Table+2

Acceptance: 57.2%

#1261Medium

Find Elements in a Contaminated Binary Tree

Binary TreeBreadth-First SearchDepth-First Search+3

Acceptance: 84.1%

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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