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If you want to master dynamic programming for coding interviews, learn these 20 patterns: 1. Fibonacci Numbers 2. 0/1 Knapsack 3. Unbounded Knapsack 4. Longest Common Subsequence 5. Longest Increasing Subsequence 6. Palindromic Subsequence 7. Matrix Chain 8. Edit Distance 9. Coin Change 10. Kadane's Algorithm 11. Grid Paths 12. Subset Sum 13. Rod Cutting 14. Climbing Stairs 15. House Robber 16. Interval DP 17. State Machine DP 18. Tree DP 19. Bitmask DP 20. Digit DP ♻️ Repost to help others in your network

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Top 15 Design Patterns You Should Know: 1. Singleton 2. Factory Method 3. Builder 4. Adapter 5. Decorator 6. Facade 7. Proxy 8. Composite 9. Observer 10. Strategy 11. Command 12. Iterator 13. State 14. Template Method 15. Chain of Responsibility Which design pattern do you use the most in your work?

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𝐇𝐨𝐰 𝐃𝐞𝐩𝐭𝐡-𝐅𝐢𝐫𝐬𝐭 𝐒𝐞𝐚𝐫𝐜𝐡 (𝐃𝐅𝐒) 𝐖𝐨𝐫𝐤𝐬: 1. 𝐒𝐭𝐚𝐫𝐭 𝐰𝐢𝐭𝐡 𝐚 𝐬𝐭𝐚𝐜𝐤: Push the source node onto a stack. Mark it as visited. 2. 𝐏𝐨𝐩 𝐭𝐡𝐞 𝐭𝐨𝐩 𝐧𝐨𝐝𝐞: Take the top element from the stack. This is the node you are currently exploring. 3. 𝐏𝐫𝐨𝐜𝐞𝐬𝐬 𝐭𝐡𝐞 𝐧𝐨𝐝𝐞: Do whatever the problem requires: print it, check a condition, record the path. 4. 𝐏𝐮𝐬𝐡 𝐮𝐧𝐯𝐢𝐬𝐢𝐭𝐞𝐝 𝐧𝐞𝐢𝐠𝐡𝐛𝐨𝐫𝐬: Look at all neighbors of the current node. For each one that has not been visited, mark it as visited and push it onto the stack. 5. 𝐑𝐞𝐩𝐞𝐚𝐭 𝐮𝐧𝐭𝐢𝐥 𝐭𝐡𝐞 𝐬𝐭𝐚𝐜𝐤 𝐢𝐬 𝐞𝐦𝐩𝐭𝐲: Go back to step 2. Each iteration goes deeper down one path before backtracking. 6. 𝐁𝐚𝐜𝐤𝐭𝐫𝐚𝐜𝐤𝐢𝐧𝐠 𝐡𝐚𝐩𝐩𝐞𝐧𝐬 𝐧𝐚𝐭𝐮𝐫𝐚𝐥𝐥𝐲: When a node has no unvisited neighbors, you do not push anything. The next pop takes you back up the path. ♻️ Repost to help others in your network

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12 must-know data structures for coding interviews: 1. 𝐀𝐫𝐫𝐚𝐲𝐬 2. 𝐌𝐚𝐭𝐫𝐢𝐱 (2𝐃 𝐀𝐫𝐫𝐚𝐲) 3. 𝐋𝐢𝐧𝐤𝐞𝐝 𝐋𝐢𝐬𝐭 4. 𝐒𝐭𝐚𝐜𝐤 5. 𝐐𝐮𝐞𝐮𝐞 6. 𝐇𝐚𝐬𝐡𝐌𝐚𝐩 7. 𝐓𝐫𝐞𝐞 8. 𝐁𝐢𝐧𝐚𝐫𝐲 𝐒𝐞𝐚𝐫𝐜𝐡 𝐓𝐫𝐞𝐞 (𝐁𝐒𝐓) 9. 𝐇𝐞𝐚𝐩 (𝐏𝐫𝐢𝐨𝐫𝐢𝐭𝐲 𝐐𝐮𝐞𝐮𝐞) 10. 𝐓𝐫𝐢𝐞 11. 𝐆𝐫𝐚𝐩𝐡 12. 𝐔𝐧𝐢𝐨𝐧-𝐅𝐢𝐧𝐝 (𝐃𝐢𝐬𝐣𝐨𝐢𝐧𝐭 𝐒𝐞𝐭) ♻️ Repost to help others preparing for interviews

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Basic OOP Concepts Explained with Clear Examples: 1. 𝐄𝐧𝐜𝐚𝐩𝐬𝐮𝐥𝐚𝐭𝐢𝐨𝐧 Hide internal data behind public methods. - Example: A BankAccount class keeps balance and pin private. The only way to interact with it is through deposit() and getBalance(). 2. 𝐀𝐛𝐬𝐭𝐫𝐚𝐜𝐭𝐢𝐨𝐧 Expose a simple interface, hide the complexity behind it. - Example: An EmailService class gives you sendEmail(to, body). Internally, it handles SMTP connections, authentication, and retry logic. The caller doesn't need to know any of that. They just call one method and it works. 3. 𝐈𝐧𝐡𝐞𝐫𝐢𝐭𝐚𝐧𝐜𝐞 Let child classes reuse and override behavior from a parent class. - Example: An Animal class defines speak(). Dog extends it and returns "Woof!", Cat extends it and returns "Meow!". Shared logic lives in one place, and each subclass customizes what it needs. 4. 𝐏𝐨𝐥𝐲𝐦𝐨𝐫𝐩𝐡𝐢𝐬𝐦 Write code that works with multiple types through a common interface. - Example: Define a Shape interface with a draw() method. Now Circle, Rectangle, and Triangle each implement draw() their own way. A single drawShape(Shape s) method works with all of them. ♻️ Repost to help others in your network

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𝐇𝐨𝐰 𝐭𝐨 𝐑𝐞𝐯𝐞𝐫𝐬𝐞 𝐚 𝐋𝐢𝐧𝐤𝐞𝐝 𝐋𝐢𝐬𝐭 (𝐕𝐢𝐬𝐮𝐚𝐥𝐢𝐳𝐞𝐝) We maintain three pointers: - prev: the previous node (initially null) - curr: the current node we are processing - next: temporarily stores the next node so we don’t lose the rest of the list At each step: - Save the next node - Reverse the current node’s pointer - Move curr and prev nodes forward Complexity: - Time Complexity: O(n) - Space Complexity: O(1)

SOLID Principles Explained with Clear Examples: 𝐒 - 𝐒𝐢𝐧𝐠𝐥𝐞 𝐑𝐞𝐬𝐩𝐨𝐧𝐬𝐢𝐛𝐢𝐥𝐢𝐭𝐲 𝐏𝐫𝐢𝐧𝐜𝐢𝐩𝐥𝐞 A class should have only one reason to change. - Example: Instead of one giant User class that handles authentication, profile updates, and sending emails, split it into UserAuth, UserProfile, and EmailService. 𝐎 - 𝐎𝐩𝐞𝐧/𝐂𝐥𝐨𝐬𝐞𝐝 𝐏𝐫𝐢𝐧𝐜𝐢𝐩𝐥𝐞 Classes should be open for extension but closed for modification. - Example: Define a Shape interface with an area() method. When you need a new shape, just add a Circle or Triangle class that implements it. 𝐋 - 𝐋𝐢𝐬𝐤𝐨𝐯 𝐒𝐮𝐛𝐬𝐭𝐢𝐭𝐮𝐭𝐢𝐨𝐧 𝐏𝐫𝐢𝐧𝐜𝐢𝐩𝐥𝐞 Subtypes must be substitutable for their base types without breaking behavior. - Example: If Bird has a fly() method, then Eagle and Sparrow should both work anywhere a Bird is expected. 𝐈 - 𝐈𝐧𝐭𝐞𝐫𝐟𝐚𝐜𝐞 𝐒𝐞𝐠𝐫𝐞𝐠𝐚𝐭𝐢𝐨𝐧 𝐏𝐫𝐢𝐧𝐜𝐢𝐩𝐥𝐞 Don't force classes to implement interfaces they don't use. - Example: Instead of one fat Machine interface with print(), scan(), and fax(), break it into Printable, Scannable, and Faxable. A SimplePrinter only implements Printable. 𝐃 - 𝐃𝐞𝐩𝐞𝐧𝐝𝐞𝐧𝐜𝐲 𝐈𝐧𝐯𝐞𝐫𝐬𝐢𝐨𝐧 𝐏𝐫𝐢𝐧𝐜𝐢𝐩𝐥𝐞 High-level modules should not depend on low-level modules. Both should depend on abstractions. - Example: Your OrderService should depend on a PaymentGateway interface, not directly on Stripe or PayPal. The real power of SOLID is not in following each principle in isolation. It's in how they work together to make your code easier to change, test, and extend. ♻️ Repost to help others in your network

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If you want to get good at System Design in 1 month, learn these 30 concepts in the next 30 days: Thread (with resources) ↴

10 Must-Know Graph Algorithms for Coding Interviews: 1. 𝐃𝐅𝐒 (𝐃𝐞𝐩𝐭𝐡-𝐅𝐢𝐫𝐬𝐭 𝐒𝐞𝐚𝐫𝐜𝐡) 2. 𝐁𝐅𝐒 (𝐁𝐫𝐞𝐚𝐝𝐭𝐡-𝐅𝐢𝐫𝐬𝐭 𝐒𝐞𝐚𝐫𝐜𝐡) 3. 𝐓𝐨𝐩𝐨𝐥𝐨𝐠𝐢𝐜𝐚𝐥 𝐒𝐨𝐫𝐭 4. 𝐔𝐧𝐢𝐨𝐧 𝐅𝐢𝐧𝐝 (𝐃𝐢𝐬𝐣𝐨𝐢𝐧𝐭 𝐒𝐞𝐭) 5. 𝐂𝐲𝐜𝐥𝐞 𝐃𝐞𝐭𝐞𝐜𝐭𝐢𝐨𝐧 6. 𝐂𝐨𝐧𝐧𝐞𝐜𝐭𝐞𝐝 𝐂𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭𝐬 7. 𝐁𝐢𝐩𝐚𝐫𝐭𝐢𝐭𝐞 𝐂𝐡𝐞𝐜𝐤 8. 𝐅𝐥𝐨𝐨𝐝 𝐅𝐢𝐥𝐥 9. 𝐌𝐢𝐧𝐢𝐦𝐮𝐦 𝐒𝐩𝐚𝐧𝐧𝐢𝐧𝐠 𝐓𝐫𝐞𝐞 10. 𝐒𝐡𝐨𝐫𝐭𝐞𝐬𝐭 𝐏𝐚𝐭𝐡 (Dijkstra) ♻️ Repost to help others in your network

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15 must-know patterns for coding interviews: 1. Prefix Sum 2. Two Pointers 3. Sliding Window 4. Fast & Slow Pointers 5. LinkedList In-place Reversal 6. Monotonic Stack 7. Top ‘K’ Elements 8. Overlapping Intervals 9. Modified Binary Search 10. Tree Traversal 11. Depth-First Search (DFS) 12. Breadth-First Search (BFS) 13. Matrix Traversal 14. Backtracking 15. Dynamic Programming Patterns ♻️ Repost to help others master coding interviews