Lesson 4.3.5.1

4.3.5.1 Bubble sort Quiz: AQA Computer Science, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.3.5.1, Bubble sort: 20 multiple choice questions for the AQA Computer Science (7517), Unit 3: Fundamentals of algorithms, written with Revision Ninja.

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The 20 questions

  1. What is the time complexity of bubble sort?

    • O(n log n)
    • O(n)
    • O(n^2)
    • O(log n)

  2. In bubble sort, what happens to adjacent items that are out of order?

    • They are swapped
    • They are merged
    • They are ignored
    • They are deleted

  3. After one complete pass of bubble sort, what is guaranteed?

    • The list is fully sorted
    • The smallest item is at the front
    • The list is reversed
    • The largest item has reached its final position at the end

  4. Why does the specification describe bubble sort as an inefficient sorting algorithm?

    • It cannot sort numbers
    • It uses too much memory
    • It is time-inefficient, with O(n^2) growth in comparisons
    • It requires a tree structure

  5. How does bubble sort work?

    • It inserts each item into a binary tree
    • It splits the list in half and merges sorted halves
    • It selects the middle item and partitions around it
    • It repeatedly compares adjacent pairs and swaps those that are out of order

  6. Which sorting algorithm is included in the specification as a particularly inefficient example?

    • Binary tree sort
    • Merge sort
    • Dijkstra sort
    • Bubble sort

  7. Bubble sort is applied to [5, 1, 4, 2, 8]. What is the list after the first pass?

    • [1, 5, 4, 2, 8]
    • [1, 2, 4, 5, 8]
    • [1, 4, 2, 5, 8]
    • [5, 1, 4, 2, 8]

  8. Bubble sort is applied to [5, 1, 4, 2, 8]. What is the list after two passes?

    • [1, 2, 4, 5, 8]
    • [2, 1, 4, 5, 8]
    • [1, 4, 2, 5, 8]
    • [1, 2, 4, 8, 5]

  9. How many swaps does bubble sort perform in total while sorting [5, 1, 4, 2, 8]?

    • 4
    • 3
    • 5
    • 2

  10. How many comparisons are made in the first pass of bubble sort on a list of 10 items?

    • 8
    • 9
    • 45
    • 10

  11. How many comparisons does a complete bubble sort of n items make without an early-exit check?

    • n + 1
    • log2 n
    • 2n
    • n(n - 1) / 2

  12. With an early-exit check that stops when a pass makes no swaps, how many passes are needed to confirm an already sorted list of 10 items?

    • 10
    • 1
    • 9
    • 2

  13. If the number of items in a bubble sort doubles, roughly how does the running time change?

    • It doubles
    • It increases by a fixed amount
    • It roughly quadruples
    • It is unchanged

  14. How many swaps does bubble sort need to sort the reverse-ordered list [4, 3, 2, 1]?

    • 3
    • 10
    • 6
    • 4

  15. For a list of 100 distinct items in reverse order, how many swaps does bubble sort perform?

    • 4950
    • 99
    • 100
    • 9900

  16. Which statement best explains why bubble sort is a poor choice for a list of one million items?

    • It requires the list to be stored as a tree
    • It uses too much memory
    • It cannot sort numbers
    • Its roughly n^2 comparisons grow far faster than n log n, making run time impractical

  17. When bubble sort compares two equal adjacent values, what should it do to keep the sort stable?

    • Leave them in place
    • Compare them with a third value
    • Swap them so their order is reversed
    • Delete one of them

  18. Bubble sort is applied to [3, 7, 2]. What is the list after the first pass?

    • [2, 3, 7]
    • [3, 7, 2]
    • [3, 2, 7]
    • [7, 3, 2]

  19. Roughly how many comparisons does a worst-case bubble sort of 1024 items make?

    • 1,048,576
    • 523,776
    • 10,240
    • 1,023

  20. A bubble sort is applied to a list that is already sorted, without the early-exit optimisation. How many swaps occur?

    • 0
    • n - 1
    • 1
    • n(n - 1) / 2

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