WGU C949 – Data Structures and Algorithms Objective Assessment | OA V1 and
V2 |Questions and Answers | 2026 Update | 100% correct.
Section 1: Algorithm Analysis & Big-O (1–20)
1. What does Big-O notation describe?
Answer: The upper bound (worst-case) time or space complexity of an algorithm.
2. Which Big-O represents constant time?
Answer: O(1)
3. What is the time complexity of binary search?
Answer: O(log n)
4. Which algorithm has O(n²) complexity in its worst case?
Answer: Bubble sort
5. What is the best-case time complexity of insertion sort?
Answer: O(n)
6. What does O(n log n) commonly represent?
Answer: Efficient comparison-based sorting algorithms (e.g., merge sort)
7. Which is faster as n grows large: O(n) or O(log n)?
Answer: O(log n)
8. What is the worst-case time complexity of quicksort?
Answer: O(n²)
9. What is the average-case time complexity of quicksort?
Answer: O(n log n)
10. Which Big-O ignores constants and lower-order terms?
Answer: Asymptotic notation
11. What is space complexity?
Answer: Memory required by an algorithm as input size grows
12. What is the time complexity of accessing an array element by index?
Answer: O(1)
13. What does exponential time complexity look like?
Answer: O(2ⁿ)
14. Which complexity is most efficient for large inputs?
Answer: O(1)
15. What is the time complexity of traversing a linked list?
Answer: O(n)
16. Which notation describes best-case complexity?
Answer: Ω (Omega)
17. Which notation describes average-case complexity?
Answer: Θ (Theta)
18. What happens to runtime when input size doubles in O(n²)?
Answer: Runtime increases by a factor of four
,19. Which algorithm has O(n log n) in all cases?
Answer: Merge sort
20. What is amortized analysis used for?
Answer: Averaging cost of operations over time
Section 2: Arrays & Strings (21–35)
21. What is an array?
Answer: A contiguous block of memory storing elements of the same type
22. What is the time complexity of inserting into the middle of an array?
Answer: O(n)
23. What is the advantage of arrays?
Answer: Fast indexed access
24. What is the main limitation of arrays?
Answer: Fixed size
25. What is a dynamic array?
Answer: An array that resizes automatically (e.g., ArrayList)
26. What happens when a dynamic array resizes?
Answer: Elements are copied to a larger array
27. What is string immutability?
Answer: Strings cannot be changed after creation
28. Why is string concatenation expensive?
Answer: It creates new objects
29. Which structure is best for frequent string modifications?
Answer: StringBuilder (or equivalent)
30. What is the time complexity of checking string length?
Answer: O(1)
31. What is the time complexity of comparing two strings of length n?
Answer: O(n)
32. What is a multidimensional array?
Answer: An array containing other arrays
33. What is the space complexity of a 2D array n × n?
Answer: O(n²)
34. What is cache locality?
Answer: Efficient memory access due to contiguous storage
,35. Which structure provides better cache performance?
Answer: Arrays
Section 3: Linked Lists (36–50)
36. What is a linked list?
Answer: A collection of nodes connected by pointers
37. What is the main advantage of linked lists over arrays?
Answer: Efficient insertion and deletion
38. What is the time complexity to insert at the head of a linked list?
Answer: O(1)
39. What is the time complexity to search a linked list?
Answer: O(n)
40. What is a singly linked list?
Answer: Each node points to the next node only
41. What is a doubly linked list?
Answer: Nodes have pointers to both next and previous nodes
42. What is a circular linked list?
Answer: The last node points back to the first
43. What is the space overhead of linked lists?
Answer: Extra memory for pointers
44. Which list allows traversal in both directions?
Answer: Doubly linked list
45. What is required to delete a node in a singly linked list?
Answer: Access to the previous node
46. What is the head of a linked list?
Answer: The first node
47. What is the tail of a linked list?
Answer: The last node
48. Which operation is slower in linked lists than arrays?
Answer: Random access
49. What is the time complexity of deleting the head node?
Answer: O(1)
50. What happens if the head pointer is lost?
Answer: The entire list becomes inaccessible
, Section 4: Stacks & Queues (51–65)
51. What is a stack?
Answer: A LIFO (Last In, First Out) data structure
52. What operations define a stack?
Answer: Push and Pop
53. What is the time complexity of stack operations?
Answer: O(1)
54. What is a queue?
Answer: A FIFO (First In, First Out) data structure
55. What operations define a queue?
Answer: Enqueue and Dequeue
56. What is a circular queue?
Answer: A queue that wraps around to reuse space
57. What is a deque?
Answer: Double-ended queue
58. Which structure is used for function calls?
Answer: Stack
59. Which structure is used for task scheduling?
Answer: Queue
60. What causes stack overflow?
Answer: Exceeding stack memory limits
61. What causes queue overflow?
Answer: No available space for insertion
62. Which structure supports backtracking?
Answer: Stack
63. What is the time complexity of enqueue?
Answer: O(1)
64. What is the time complexity of dequeue?
Answer: O(1)
65. Which data structure is best for BFS?
Answer: Queue
V2 |Questions and Answers | 2026 Update | 100% correct.
Section 1: Algorithm Analysis & Big-O (1–20)
1. What does Big-O notation describe?
Answer: The upper bound (worst-case) time or space complexity of an algorithm.
2. Which Big-O represents constant time?
Answer: O(1)
3. What is the time complexity of binary search?
Answer: O(log n)
4. Which algorithm has O(n²) complexity in its worst case?
Answer: Bubble sort
5. What is the best-case time complexity of insertion sort?
Answer: O(n)
6. What does O(n log n) commonly represent?
Answer: Efficient comparison-based sorting algorithms (e.g., merge sort)
7. Which is faster as n grows large: O(n) or O(log n)?
Answer: O(log n)
8. What is the worst-case time complexity of quicksort?
Answer: O(n²)
9. What is the average-case time complexity of quicksort?
Answer: O(n log n)
10. Which Big-O ignores constants and lower-order terms?
Answer: Asymptotic notation
11. What is space complexity?
Answer: Memory required by an algorithm as input size grows
12. What is the time complexity of accessing an array element by index?
Answer: O(1)
13. What does exponential time complexity look like?
Answer: O(2ⁿ)
14. Which complexity is most efficient for large inputs?
Answer: O(1)
15. What is the time complexity of traversing a linked list?
Answer: O(n)
16. Which notation describes best-case complexity?
Answer: Ω (Omega)
17. Which notation describes average-case complexity?
Answer: Θ (Theta)
18. What happens to runtime when input size doubles in O(n²)?
Answer: Runtime increases by a factor of four
,19. Which algorithm has O(n log n) in all cases?
Answer: Merge sort
20. What is amortized analysis used for?
Answer: Averaging cost of operations over time
Section 2: Arrays & Strings (21–35)
21. What is an array?
Answer: A contiguous block of memory storing elements of the same type
22. What is the time complexity of inserting into the middle of an array?
Answer: O(n)
23. What is the advantage of arrays?
Answer: Fast indexed access
24. What is the main limitation of arrays?
Answer: Fixed size
25. What is a dynamic array?
Answer: An array that resizes automatically (e.g., ArrayList)
26. What happens when a dynamic array resizes?
Answer: Elements are copied to a larger array
27. What is string immutability?
Answer: Strings cannot be changed after creation
28. Why is string concatenation expensive?
Answer: It creates new objects
29. Which structure is best for frequent string modifications?
Answer: StringBuilder (or equivalent)
30. What is the time complexity of checking string length?
Answer: O(1)
31. What is the time complexity of comparing two strings of length n?
Answer: O(n)
32. What is a multidimensional array?
Answer: An array containing other arrays
33. What is the space complexity of a 2D array n × n?
Answer: O(n²)
34. What is cache locality?
Answer: Efficient memory access due to contiguous storage
,35. Which structure provides better cache performance?
Answer: Arrays
Section 3: Linked Lists (36–50)
36. What is a linked list?
Answer: A collection of nodes connected by pointers
37. What is the main advantage of linked lists over arrays?
Answer: Efficient insertion and deletion
38. What is the time complexity to insert at the head of a linked list?
Answer: O(1)
39. What is the time complexity to search a linked list?
Answer: O(n)
40. What is a singly linked list?
Answer: Each node points to the next node only
41. What is a doubly linked list?
Answer: Nodes have pointers to both next and previous nodes
42. What is a circular linked list?
Answer: The last node points back to the first
43. What is the space overhead of linked lists?
Answer: Extra memory for pointers
44. Which list allows traversal in both directions?
Answer: Doubly linked list
45. What is required to delete a node in a singly linked list?
Answer: Access to the previous node
46. What is the head of a linked list?
Answer: The first node
47. What is the tail of a linked list?
Answer: The last node
48. Which operation is slower in linked lists than arrays?
Answer: Random access
49. What is the time complexity of deleting the head node?
Answer: O(1)
50. What happens if the head pointer is lost?
Answer: The entire list becomes inaccessible
, Section 4: Stacks & Queues (51–65)
51. What is a stack?
Answer: A LIFO (Last In, First Out) data structure
52. What operations define a stack?
Answer: Push and Pop
53. What is the time complexity of stack operations?
Answer: O(1)
54. What is a queue?
Answer: A FIFO (First In, First Out) data structure
55. What operations define a queue?
Answer: Enqueue and Dequeue
56. What is a circular queue?
Answer: A queue that wraps around to reuse space
57. What is a deque?
Answer: Double-ended queue
58. Which structure is used for function calls?
Answer: Stack
59. Which structure is used for task scheduling?
Answer: Queue
60. What causes stack overflow?
Answer: Exceeding stack memory limits
61. What causes queue overflow?
Answer: No available space for insertion
62. Which structure supports backtracking?
Answer: Stack
63. What is the time complexity of enqueue?
Answer: O(1)
64. What is the time complexity of dequeue?
Answer: O(1)
65. Which data structure is best for BFS?
Answer: Queue
