🌱 Keegan's Digital Garden
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Algorithm Design Manual
01. Introduction to Algorithm Design
02. Algorithm Analysis
03. Data Structures
04. Sorting and Searching
05. Graph Traversal
06. Weighted Graph Algorithms
07. Combinatorial Search & Heuristic Methods
08. Dynamic Programming
09. Intractable Problems & Approximation Algorithms
10. How to Design Algorithms
Cracking the Coding Interview
01. Arrays & Strings
02. Linked Lists
03. Stacks & Queues
04. Trees & Graphs
05. Bit Manipulation
06. Math & Logic Puzzles
07. Object-Oriented Design
08. Recursion & Dynamic Programming
09. System Design & Scalability
10. Sorting & Searching
11. Testing
12. C & C++
13. Java
14. Databases
15. Threads & Locks
Tao Te Ching
Notes
Quotes
Themes
2025 Reading List
Career & Wisdom
Communicating Complex Ideas
Context-Driven Decision Making
Excelling as a Junior
Optimizing for Humans
Sharing Knowledge
The Grug Brained Developer
Data Structures & Algorithms
Problems
🗣 Mock Revision
19. Remove Nth Node From End of List
20. Valid Parentheses
58. Length of Last Word
61. Rotate List
66. Plus One
74. Search a 2D Matrix
104. Maximum Depth of Binary Tree
118. Pascal's Triangle
122. Best Time to Buy and Sell Stock II
130. Surrounded Regions
169. Majority Element
199. Binary Tree Right Side View
268. Missing Number
345. Reverse Vowels of a String
355. Design Twitter
380. Insert Delete GetRandom O(1)
456. 132 Pattern
565. Array Nesting
650. Keys Keyboard
867. Transpose Matrix
978. Longest Turbulent Subarray
1014. Best Sightseeing Pair
1025. Divisor Game
1046. Last Stone Weight
1287. Element Appearing More Than 25% In Sorted Array
1346. Check if N and Its Double Exist
1422. Maximum Score After Splitting a String
1561. Maximum Number of Coins You Can Get
1685. Sum of Absolute Differences in a Sorted Array
1688. Count of Matches in Tournament
1725. Number of Rectangles That Can Form The Largest Square
2109. Adding Spaces to a String
2116. Check if a Parentheses String Can Be Valid
2160. Minimum Sum of Four Digit Number After Splitting Digits
2181. Merge Nodes in Between Zeros
3079. Find the Sum of Encrypted Integers
🧠 Neetcode 150
01. Arrays & Hashing
36. Valid Sudoku
128. Longest Consecutive Sequence
02. Two Pointers
11. Container With Most Water
42. Trapping Rain Water
03. Sliding Window
76. Minimum Window Substring
239. Sliding Window Maximum
04. Stacks
20. Valid Parentheses
22. Generate Parentheses
84. Largest Rectangle in Histogram
150. Evaluate Reverse Polish Notation
155. Min Stack
739. Daily Temperatures
853. Car Fleet
05. Linked Lists
2. Add Two Numbers
19. Remove Nth Node From End of List
21. Merge Two Sorted Lists
23. Merge k Sorted Lists
25. Reverse Nodes in k-Group
138. Copy List with Random Pointer
141. Linked List Cycle
143. Reorder List
146. LRU Cache
206. Reverse Linked List
287. Find the Duplicate Number
06. Binary Search
4. Median of Two Sorted Arrays
33. Search in Rotated Sorted Array
74. Search a 2D Matrix
153. Find Minimum in Rotated Sorted Array
704. Binary Search
875. Koko Eating Bananas
981. Time Based Key-Value Store
07. Trees
98. Validate Binary Search Tree
100. Same Tree
102. Binary Tree Level Order Traversal
104. Maximum Depth of Binary Tree
105. Construct Binary Tree from Preorder and Inorder Traversal
110. Balanced Binary Tree
199. Binary Tree Right Side View
226. Invert Binary Tree
230. Kth Smallest Element in a BST
235. Lowest Common Ancestor of a Binary Search Tree
543. Diameter of Binary Tree
572. Subtree of Another Tree
1448. Count Nodes in Binary Tree
08. Backtracking
17. Letter Combinations of a Phone Number
39. Combination Sum
40. Combination Sum II
46. Permutations
51. N-Queens
78. Subsets
79. Word Search
90. Subsets II
131. Palindrome Partitioning
09. 1D Dynamic Programming
5. Longest Palindromic Substring
70. Climbing Stairs
91. Decode Ways
139. Word Break
152. Maximum Product Subarray
198. House Robber
213. House Robber II
300. Longest Increasing Subsequence
322. Coin Change
416. Partition Equal Subset Sum
647. Palindromic Substrings
746. Min Cost Climbing Stairs
10. Graphs
130. Surrounded Regions
133. Clone Graph
200. Number of Islands
207. Course Schedule
210. Course Schedule II
261. Graph Valid Tree
286. Walls and Gates
323. Number of Connected Components in an Undirected Graph
417. Pacific Atlantic Water Flow
684. Redundant Connection
695. Max Area of Island
994. Rotting Oranges
11. Greedy
45. Jump Game II
53. Maximum Subarray
55. Jump Game
134. Gas Station
678. Valid Parenthesis String
763. Partition Labels
846. Hand of Straights
1899. Merge Triplets to Form Target Triplet
12. 2D Dynamic Programming
62. Unique Paths
309. Best Time to Buy and Sell Stock with Cooldown
518. Coin Change II
1143. Longest Common Subsequence
🧩 LeetCode
Week 1
15. 3Sum
33. Search in Rotated Sorted Array
56. Merge Intervals
188. Best Time to Buy and Sell Stock IV
691. Stickers to Spell Word
1309. Decrypt String from Alphabet to Integer Mapping
1323. Maximum 69 Number
2265. Count Nodes Equal To Average of Subtree
2328. Number of Increasing Paths in a Grid
2555. Maximize Win From Two Segments
Week 2
2. Add Two Numbers
438. Find All Anagrams in a String
623. Add One Row to Tree
725. Split Linked List in Parts
1220. Count Vowels Permutation
1349. Maximum Students Taking Exam
1547. Minimum Cost to Cut a Stick
1652. Defuse the Bomb
1961. Check If String Is a Prefix of Array
3342. Find Minimum Time to Reach Last Room II
Week 3
18. 4Sum
54. Spiral Matrix
309. Best Time to Buy and Sell Stock with Cooldown
679. 24 Game
778. Swim in Rising Water
1172. Dinner Plate Stacks
1457. Pseudo-Palindromic Paths in a Binary Tree
1528. Shuffle String
1981. Minimize the Difference Between Target and Chosen Elements
1984. Minimum Difference Between Highest and Lowest of K Scores
Week 4
65. Unique Paths II
71. Simplify Path
203. Remove Linked List Elements
330. Patching Array
448. Find all Numbers Disappeared in an Array
507. Perfect Number
740. Delete and Earn
989. Add to Array-Form of Integer
1962. Remove Stones to Minimize the Total
2091. Removing Minimum and Maximum From Array
Week 5
🎅Break this week ~ hohoho
Week 6
590. N-ary Tree Postorder Traversal
643. Maximum Average Subarray I
860. Lemonade Change
877. Stone Game
1094. Car Pooling
1124. Longest Well-Performing Interval
1237. Find Positive Integer Solution for a Given Equation
1238. Circular Permutation in Binary Representation
2325. Decode the Message
2331. Evaluate Boolean Binary Tree
Week 7
133. Clone Graph
929. Unique Email Addresses
1054. Distant Barcodes
1130. Minimum Cost Tree From Leaf Values
1379. Find a Corresponding Node of a Binary Tree in a Clone of That Tree
1530. Number of Good Leaf Nodes Pairs
1588. Sum of All Odd Length Subarrays
1605. Find Valid Matrix Given Row and Column Sums
2009. Minimum Number of Operations to Make Array Contiguous
2642. Design Graph With Shortest Path Calculator
Week 8
204. Count Primes
518. Coin Change II
1486. XOR Operation in an Array
1494. Parallel Courses II
1569. Number of Ways to Reorder Array to Get Same BST
2207. Maximize Number of Subsequences in a String
2304. Minimum Path Cost in a Grid
2365. Task Scheduler II
2591. Distribute Money to Maximum Children
3184. Count Pairs That Form a Complete Day I
Week 9
30. Substring with Concatenation of All Words
322. Coin Change
433. Minimum Genetic Mutation
563. Binary Tree Tilt
1154. Day of the Year
1202. Smallest String With Swaps
2244. Minimum Rounds to Complete All Tasks
2256. Minimum Average Difference
2872. Maximum Number of K-Divisible Components
2980. Check if Bitwise OR Has Trailing Zeros
Week 10
363. Max Sum of Rectangle No Larger Than K
461. Hamming Distance
703. Kth Largest Element in a Stream
1277. Count Square Submatrices with All Ones
1299. Replace Elements With Greatest Element on Right Side
1305. All Elements in Two Binary Search Trees
1353. Maximum Number of Events That Can Be Attended
1815. Maximum Number of Groups Getting Fresh Donuts
2310. Sum of Numbers With Units Digit K
3223. Minimum Length of String After Operations
Week 11
52. N-Queens II
174. Dungeon Game
Technical Interview Checklist
Theory
Graphs
Bellman-Ford Pathfinding Algorithm
Dijkstra's Shortest Path Algorithm
Graph Traversal
Graphs
Minimum Spanning Tree
Topological Sort
Union-Find (Disjoint Set)
Linked Lists
Circular Linked List
Doubly Linked List
Linked List
Math
Greatest Common Divisor (GCD)
Sieve of Eratosthenes (Prime number generation)
Queues
Deque (Double-Ended-Queue)
Priority Queue
Queue
Sorting
Heap Sort
Insertion Sort
Merge Sort
Quick Sort
Trees
Balanced BST
AVL Tree
Binary Search Tree (BST)
Red-Black Trees
Rotations in Balanced BSTs
Binary Tree
Heap
Tree Traversal
Trie (Prefix Tree)
Two Pointers
Sliding Window
Slow and Fast Pointers
Two Pointers
Backtracking
Binary Search
Bit Manipulation
Dynamic Programming
Kadane's Algorithm
Monotonic Stack
Prefix Sum
Quick Select
Vector Amortized Time
Engineering
APIs
Authentication
API Keys
JWT
OAuth2
Rate Limiting
API Gateways
GraphQL
gRPC
REST
RPC
The Essence of API Design
WebSockets
Cloud
AWS
Cloud Computing Explained
Infrastructure as Code (IaC)
Microservices
Monoliths
Server vs. Serverless
Databases
Caching
Indexes
Normalization vs. Denormalization
Query Optimization
Replication
Sharding
SQL vs. NoSQL
Design Patterns
Architectural Patterns
Event-Driven Architecture
Microservices
Model-View-Controller (MVC)
Model-View-ViewModel (MVVM)
Behavioural Patterns
Chain of Responsibility
Command
Iterator
Mediator
Memento
Observer
State
Strategy
Template Method
Visitor
Concurrency Patterns
Event Loop
Future - Promise
Producer - Consumer
Read-Write Lock
Thread Pool
Creational Patterns
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Builder
Factory Method
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Structural Patterns
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Bridge
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Flyweight
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Languages
Swift
Combine
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Combine Latest
Operators
Zip
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Combine
Publishers
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Subjects
Subscribers
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Action Operations
Actions
Lens
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Redux
Store
Thunk
View
Swift Concepts
Actor
Concurrency
Delegate
Executor
MainActor
JavaScript
Python
TypeScript
Programming Paradigms
Functional Programming
Functional Reactive Programming
Object-Oriented Programming
Procedural Programming
Technologies
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Express.js
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Microsoft .NET Framework
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Next.js
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Home
❯
Data Structures and Algorithms
❯
Problems
❯
🧠 Neetcode 150
❯
05. Linked Lists
❯
2. Add Two Numbers
2. Add Two Numbers
Mar 14, 2025
1 min read
*already solved as a mock interview question~ see
2. Add Two Numbers
Graph View