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
167. Two Sum II - Input Array Is Sorted	Medium	65.5%	Array Binary Search+1	Read
172. Factorial Trailing Zeroes	Medium	46.9%	Math	Read
173. Binary Search Tree Iterator	Medium	76.9%	Binary Search Tree Binary Tree+4	Read
176. Second Highest Salary	Medium	42.2%	Database	Read
177. Nth Highest Salary	Medium	38.0%	Database	Read
178. Rank Scores	Medium	63.9%	Database	Read
179. Largest Number	Medium	43.3%	Array Greedy+2	Read
180. Consecutive Numbers	Medium	44.6%	Database	Read
184. Department Highest Salary	Medium	53.2%	Database	Read
186. Reverse Words in a String II	Medium	56.6%	String Two Pointers	Read
187. Repeated DNA Sequences	Medium	53.7%	Bit Manipulation Hash Function+4	Read
189. Rotate Array	Medium	45.3%	Array Math+1	Read
192. Word Frequency	Medium	26.3%	Shell	Read
194. Transpose File	Medium	27.1%	Shell	Read
198. House Robber	Medium	53.6%	Array Dynamic Programming	Read
199. Binary Tree Right Side View	Medium	70.9%	Binary Tree Breadth-First Search+2	Read
200. Number of Islands	Medium	65.2%	Array Breadth-First Search+3	Read
201. Bitwise AND of Numbers Range	Medium	48.8%	Bit Manipulation	Read
204. Count Primes	Medium	36.4%	Array Enumeration+2	Read
207. Course Schedule	Medium	52.2%	Breadth-First Search Depth-First Search+2	Read
208. Implement Trie (Prefix Tree)	Medium	69.9%	Design Hash Table+2	Read
209. Minimum Size Subarray Sum	Medium	52.5%	Array Binary Search+2	Read
210. Course Schedule II	Medium	56.3%	Breadth-First Search Depth-First Search+2	Read
211. Design Add and Search Words Data Structure	Medium	48.9%	Depth-First Search Design+2	Read
213. House Robber II	Medium	45.3%	Array Dynamic Programming	Read
215. Kth Largest Element in an Array	Medium	68.8%	Array Divide and Conquer+3	Read
216. Combination Sum III	Medium	73.6%	Array Backtracking	Read
221. Maximal Square	Medium	50.7%	Array Dynamic Programming+1	Read
222. Count Complete Tree Nodes	Medium	72.6%	Binary Search Binary Tree+2	Read
223. Rectangle Area	Medium	50.3%	Geometry Math	Read
227. Basic Calculator II	Medium	46.7%	Math Stack+1	Read
229. Majority Element II	Medium	56.5%	Array Counting+2	Read
230. Kth Smallest Element in a BST	Medium	77.2%	Binary Search Tree Binary Tree+2	Read
235. Lowest Common Ancestor of a Binary Search Tree	Medium	71.4%	Binary Search Tree Binary Tree+2	Read
236. Lowest Common Ancestor of a Binary Tree	Medium	70.1%	Binary Tree Depth-First Search+1	Read
237. Delete Node in a Linked List	Medium	84.3%	Linked List	Read
238. Product of Array Except Self	Medium	69.3%	Array Prefix Sum	Read
240. Search a 2D Matrix II	Medium	57.6%	Array Binary Search+2	Read
241. Different Ways to Add Parentheses	Medium	73.7%	Dynamic Programming Math+3	Read
244. Shortest Word Distance II	Medium	62.8%	Array Design+3	Read
245. Shortest Word Distance III	Medium	59.4%	Array String	Read
247. Strobogrammatic Number II	Medium	53.5%	Array Recursion+1	Read
249. Group Shifted Strings	Medium	67.8%	Array Hash Table+1	Read
250. Count Univalue Subtrees	Medium	57.5%	Binary Tree Depth-First Search+1	Read
251. Flatten 2D Vector	Medium	50.5%	Array Design+2	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
259. 3Sum Smaller	Medium	51.4%	Array Binary Search+2	Read

#167Medium

Two Sum II - Input Array Is Sorted

ArrayBinary SearchTwo Pointers

Acceptance: 65.5%

#172Medium

Factorial Trailing Zeroes

Math

Acceptance: 46.9%

#173Medium

Binary Search Tree Iterator

Binary Search TreeBinary TreeDesign+3

Acceptance: 76.9%

#176Medium

Second Highest Salary

Database

Acceptance: 42.2%

#177Medium

Nth Highest Salary

Database

Acceptance: 38.0%

#178Medium

Rank Scores

Database

Acceptance: 63.9%

#179Medium

Largest Number

ArrayGreedySorting+1

Acceptance: 43.3%

#180Medium

Consecutive Numbers

Database

Acceptance: 44.6%

#184Medium

Department Highest Salary

Database

Acceptance: 53.2%

#186Medium

Reverse Words in a String II

StringTwo Pointers

Acceptance: 56.6%

#187Medium

Repeated DNA Sequences

Bit ManipulationHash FunctionHash Table+3

Acceptance: 53.7%

#189Medium

Rotate Array

ArrayMathTwo Pointers

Acceptance: 45.3%

#192Medium

Word Frequency

Shell

Acceptance: 26.3%

#194Medium

Transpose File

Shell

Acceptance: 27.1%

#198Medium

House Robber

ArrayDynamic Programming

Acceptance: 53.6%

#199Medium

Binary Tree Right Side View

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 70.9%

#200Medium

Number of Islands

ArrayBreadth-First SearchDepth-First Search+2

Acceptance: 65.2%

#201Medium

Bitwise AND of Numbers Range

Bit Manipulation

Acceptance: 48.8%

#204Medium

Count Primes

ArrayEnumerationMath+1

Acceptance: 36.4%

#207Medium

Course Schedule

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 52.2%

#208Medium

Implement Trie (Prefix Tree)

DesignHash TableString+1

Acceptance: 69.9%

#209Medium

Minimum Size Subarray Sum

ArrayBinary SearchPrefix Sum+1

Acceptance: 52.5%

#210Medium

Course Schedule II

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 56.3%

#211Medium

Design Add and Search Words Data Structure

Depth-First SearchDesignString+1

Acceptance: 48.9%

#213Medium

House Robber II

ArrayDynamic Programming

Acceptance: 45.3%

#215Medium

Kth Largest Element in an Array

ArrayDivide and ConquerHeap (Priority Queue)+2

Acceptance: 68.8%

#216Medium

Combination Sum III

ArrayBacktracking

Acceptance: 73.6%

#221Medium

Maximal Square

ArrayDynamic ProgrammingMatrix

Acceptance: 50.7%

#222Medium

Count Complete Tree Nodes

Binary SearchBinary TreeBit Manipulation+1

Acceptance: 72.6%

#223Medium

Rectangle Area

GeometryMath

Acceptance: 50.3%

#227Medium

Basic Calculator II

MathStackString

Acceptance: 46.7%

#229Medium

Majority Element II

ArrayCountingHash Table+1

Acceptance: 56.5%

#230Medium

Kth Smallest Element in a BST

Binary Search TreeBinary TreeDepth-First Search+1

Acceptance: 77.2%

#235Medium

Lowest Common Ancestor of a Binary Search Tree

Binary Search TreeBinary TreeDepth-First Search+1

Acceptance: 71.4%

#236Medium

Lowest Common Ancestor of a Binary Tree

Binary TreeDepth-First SearchTree

Acceptance: 70.1%

#237Medium

Delete Node in a Linked List

Linked List

Acceptance: 84.3%

#238Medium

Product of Array Except Self

ArrayPrefix Sum

Acceptance: 69.3%

#240Medium

Search a 2D Matrix II

ArrayBinary SearchDivide and Conquer+1

Acceptance: 57.6%

#241Medium

Different Ways to Add Parentheses

Dynamic ProgrammingMathMemoization+2

Acceptance: 73.7%

#244Medium

Shortest Word Distance II

ArrayDesignHash Table+2

Acceptance: 62.8%

#245Medium

Shortest Word Distance III

ArrayString

Acceptance: 59.4%

#247Medium

Strobogrammatic Number II

ArrayRecursionString

Acceptance: 53.5%

#249Medium

Group Shifted Strings

ArrayHash TableString

Acceptance: 67.8%

#250Medium

Count Univalue Subtrees

Binary TreeDepth-First SearchTree

Acceptance: 57.5%

#251Medium

Flatten 2D Vector

ArrayDesignIterator+1

Acceptance: 50.5%

#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%

#259Medium

3Sum Smaller

ArrayBinary SearchSorting+1

Acceptance: 51.4%

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Master DSA with Step-by-Step Solutions

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