Top 50 Coding Interview Questions 💻🚀

1. What is the time and space complexity of your code?
2. Difference between array and linked list.
3. How does a HashMap work internally?
4. What is recursion? Give an example.
5. Explain stack vs. queue.
6. What is a binary search and when to use it?
7. Difference between BFS and DFS.
8. What is dynamic programming?
9. Solve Fibonacci using memoization.
10. Explain two-pointer technique with an example.
11. What is a sliding window algorithm?
12. Detect cycle in a linked list.
13. Find the intersection of two arrays.
14. Reverse a string or linked list.
15. Check if a string is a palindrome.
16. What are the different sorting algorithms?
17. Explain quicksort vs. mergesort.
18. What is a binary search tree (BST)?
19. Inorder, Preorder, Postorder traversals.
20. Implement LRU Cache.
21. Find the longest substring without repeating characters.
22. Explain backtracking with N-Queens problem.
23. What is a trie? Where is it used?
24. Explain bit manipulation tricks.
25. Kadane’s Algorithm for maximum subarray sum.
26. What are heaps and how do they work?
27. Find kth largest element in an array.
28. How to detect cycle in a graph?
29. Topological sort of a DAG.
30. Implement a stack using queues.
31. Explain the difference between pass by value and reference.
32. What is memoization vs. tabulation?
33. Solve the knapsack problem.
34. Find duplicate numbers in an array.
35. What are function closures in Python/JavaScript?
36. How does garbage collection work in Java?
37. What are lambda functions?
38. Explain OOPs concepts: Inheritance, Polymorphism, Encapsulation, Abstraction.
39. What is multithreading vs. multiprocessing?
40. Difference between process and thread.
41. Implement a binary heap.
42. Explain prefix sum technique.
43. Design a parking lot system.
44. Find median in a stream of numbers.
45. Detect anagram strings.
46. Serialize and deserialize a binary tree.
47. Implement a trie with insert and search.
48. Explain design patterns like Singleton, Factory.
49. Discuss trade-offs between readability and performance.
50. How do you debug a tricky bug?

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