Real Technical Interview Questions - Continuation

Based on the pattern of your 14 actual interview questions, here are similar specific, practical
questions:

Python/NumPy Specific Implementation Questions

15. What does np.where(arr > 5, arr, 0) do?

Answer: Replaces elements ≤ 5 with 0, keeps elements > 5 unchanged

16. What's the difference between np.array([1,2,3]).reshape(-1,1) and

np.array([1,2,3]).reshape(1,-1) ?

Answer: First creates column vector (3x1), second creates row vector (1x3)

17. What does pd.DataFrame.groupby('column').agg({'col1': 'sum', 'col2': 'mean'}) do?

Answer: Groups by 'column', applies sum to col1 and mean to col2

18. What's the result of "hello".ljust(10, '*') ?

Answer: "hello*****" (left-justified with * padding)

SQL Specific Functions

19. What does COALESCE(NULL, NULL, 'default', 'second') return?

Answer: 'default' (returns first non-NULL value)

20. What's the difference between HAVING COUNT(*) > 5 and WHERE COUNT(*) > 5 ?

Answer: HAVING filters groups after GROUP BY, WHERE filters rows before grouping

21. What does SELECT DISTINCT ON (column1) column1, column2 FROM table ORDER BY
column1, column2 do in PostgreSQL?

Answer: Returns first row for each unique value of column1 based on ORDER BY

22. What's the result of SELECT '2023-01-15'::date + INTERVAL '2 months' in PostgreSQL?

Answer: 2023-03-15 (adds 2 months to the date)

JavaScript Array/Object Methods

23. What does [1,2,3].flatMap(x => [x, x*2]) return?

Answer: [1, 2, 2, 4, 3, 6] (maps then flattens)

24. What's the result of Object.entries({a: 1, b: 2}) ?

Answer: [['a', 1], ['b', 2]] (converts object to key-value pairs array)

25. What does [1,2,3].reduceRight((acc, val) => acc - val, 10) return?

Answer: 4 (10 - 3 - 2 - 1, processes from right to left)

26. What's the difference between Array.from({length: 3}, (_, i) => i) and new
Array(3).fill().map((_, i) => i) ?

Answer: Both create [0, 1, 2], but Array.from is more direct and doesn't create sparse
array

CSS/HTML Specifics
27. What's the difference between display: none and visibility: hidden ?

Answer: display: none removes element from layout, visibility: hidden keeps space but
hides element

28. What does position: sticky do?

Answer: Element is positioned relative until it crosses threshold, then becomes fixed

29. What's the specificity value of #nav ul.menu li a:hover ?

Answer: 0,1,2,2 (1 ID, 2 classes/pseudo-classes, 2 elements)

Git Commands
30. What's the difference between git reset --soft HEAD~1 and git reset --hard HEAD~1 ?

Answer: --soft keeps changes staged, --hard discards all changes

31. What does git cherry-pick <commit-hash> do?

Answer: Applies specific commit from another branch to current branch

32. What's the result of git rebase -i HEAD~3 ?

Answer: Opens interactive rebase for last 3 commits, allowing squash/edit/reorder

Data Structures Implementation Details
33. In a hash table with linear probing, what happens when collision occurs?

Answer: Checks next available slot sequentially until empty slot found

34. What's the difference between collections.deque.appendleft() and list.insert(0, item)

in Python?

Answer: deque.appendleft() is O(1), list.insert(0) is O(n)

35. In a min-heap, if parent is at index i , what are the children indices?

Answer: Left child: 2i + 1, Right child: 2i + 2 (0-based indexing)

Network/HTTP Specifics
36. What's the difference between HTTP/1.1 and HTTP/2 multiplexing?

Answer: HTTP/2 allows multiple requests simultaneously over single connection,

HTTP/1.1 processes sequentially

37. What does the Vary: Accept-Encoding header do?

Answer: Tells caches to serve different versions based on client's Accept-Encoding

header

38. What's the difference between 302 Found and 307 Temporary Redirect ?

Answer: 307 preserves HTTP method, 302 may change POST to GET

Database Indexing
39. What's the difference between clustered and non-clustered index?

Answer: Clustered index physically orders data, non-clustered is separate structure

pointing to data

40. What does EXPLAIN ANALYZE show vs just EXPLAIN ?

Answer: EXPLAIN ANALYZE actually executes query and shows real timing, EXPLAIN
shows estimated plan only

RegEx Patterns
41. What does the regex pattern ^\d{3}-\d{2}-\d{4}$ match?

Answer: Exactly XXX-XX-XXXX format (like SSN: 123-45-6789)

42. What's the difference between .* and .*? in regex?

Answer: .* is greedy (matches as much as possible), .*? is non-greedy (matches as little

as possible)

Memory Management
43. What's the difference between malloc() and calloc() in C?

Answer: malloc allocates uninitialized memory, calloc allocates zero-initialized memory

44. What happens when you delete a pointer in C++ but don't set it to nullptr?

Answer: Creates dangling pointer - pointer still holds address but memory is freed

API Design
45. What's the difference between PUT /users/123 and PATCH /users/123 ?

Answer: PUT replaces entire resource, PATCH updates specific fields only

46. What does Content-Type: multipart/form-data indicate?

Answer: Form data contains files or binary data, each part has its own content type

Algorithm Implementation
47. In quicksort, what's the worst-case scenario for pivot selection?

Answer: Always selecting smallest or largest element as pivot (already sorted array)

48. What's the space complexity of in-place heapsort?

Answer: O(1) - sorts array without additional space

More T-SQL Specific Functions (Following your YEAR pattern)

49. In T-SQL, how would you get the month from a datetime field?

Answer: MONTH(date_column)

50. What does DATEDIFF(day, '2023-01-01', '2023-01-15') return in T-SQL?

 Answer: 14 (number of days between dates)

51. What is the T-SQL function to get current date without time?

Answer: CAST(GETDATE() AS DATE) or CONVERT(DATE, GETDATE())

More C++ STL Specifics (Following your vector::reserve pattern)

52. What is the effect of calling std::vector::shrink_to_fit() ?

Answer: Reduces capacity to match size, freeing unused memory

53. What does std::map::emplace() do differently from insert() ?

Answer: Constructs element in-place, avoiding copy/move operations

54. What is the difference between std::vector::at() and operator[] ?

Answer: at() performs bounds checking and throws exception, [] doesn't check
bounds

More Networking Protocol Details (Following your BGP/DNS

pattern)
55. What is the primary purpose of OSPF (Open Shortest Path First) routing protocol?

Answer: To find shortest path within a single autonomous system using link-state
algorithm

56. Which type of DNS record is used to specify mail server for a domain?

Answer: MX (Mail Exchange) record

57. What is the default port for SMTP (Simple Mail Transfer Protocol)?

Answer: Port 25

More Algorithm Implementation Steps (Following your heap sort

pattern)
58. The first step of Quick Sort is to:

Answer: Choose a pivot element from the array

59. In Merge Sort, what happens in the "merge" step?

 Answer: Combine two sorted subarrays into one sorted array

60. What is the first operation in building a Binary Search Tree?

Answer: Insert the root node

More Math/Clock/Logic Puzzles (Following your Fibonacci/clock

pattern)
61. What is the next number in sequence: 2, 6, 12, 20, 30, ?

Answer: 42 (differences are 4, 6, 8, 10, 12 - adding consecutive even numbers)

62. A clock shows 6:00. What is the angle between hour and minute hands?

Answer: 180 degrees (straight line)

63. If it takes 5 machines 5 minutes to make 5 widgets, how long does it take 100
machines to make 100 widgets?

Answer: 5 minutes (each machine makes 1 widget in 5 minutes)

OS-Specific Commands (Following your os.listdir pattern)

64. What does the following Linux command do: find . -name "*.py" -type f ?

Answer: Find all Python files (.py) in current directory and subdirectories

65. What is the purpose of chmod +x filename in Linux?

Answer: Add execute permission to the file

66. What does ps aux | grep python do?

Answer: Show all running processes containing "python" in their command

More String/Array Operations (Following your slicing pattern)

67. What is the result of "hello world".split() in Python?

Answer: ['hello', 'world'] (splits on whitespace by default)

68. What does arr[::-1] do in Python?

Answer: Reverses the array/string (step of -1)

69. What is the output of "python"[1:4] in Python?

Answer: "yth" (characters at index 1, 2, 3)

More HTTP/Web Specifics (Following your AJAX/HTTP pattern)

70. What is the primary difference between GET and POST HTTP methods?

Answer: GET sends data in URL parameters, POST sends data in request body

71. What does HTTP status code 404 mean?

Answer: Not Found - requested resource doesn't exist on server

72. What is the purpose of CORS (Cross-Origin Resource Sharing)?

Answer: Allow web pages to make requests to different domains securely