AQA 8525 3.1.2: Efficiency of algorithms
The free BugBot lesson that teach this point, a robot to try it on, and the past-paper questions that test it.
What it covers
Bubble sort and insertion sort are simple but slow on big lists. Merge sort uses a cleverer idea: split the list into tiny pieces that are trivially sorted, then merge sorted pieces together, again and again, until one sorted list is left. It is much faster on big lists, and the idea behind it, divide and conquer, is one of the most important in computing. This lesson also compares all the algorithms in the module.
- Merging two sorted lists
- Splitting and merging
- Comparing the sorts
- Choosing an algorithm
Or do it in the simulator, with tasks that mark themselves
Lessons that teach it
- F5.9 Merge sort and comparing algorithms Algorithms
Splitting and merging, and choosing between the searches and sorts.
Try it on a robot
The task from F5.9 Merge sort and comparing algorithms, running here. Change the program and press Run.
Past paper questions on this
Real exam questions that test this, each worked through with a program you can run.
- AQA 8525 June 2025 Paper 1, Question 6: Show a bubble sort and a merge, compare them, and justify a binary search 10 marks
- AQA 8525 June 2022 Paper 1, Question 4: Which of two programs is more efficient, and why 3 marks
- OCR J277 June 2025 Paper 2, Question 3(a): Show the steps of a merge sort on eight numbers 4 marks
- OCR J277 June 2024 Paper 2, Question 3(c): Show a binary search for 10, its pre-requisite, and name merge sort 5 marks
- OCR J277 June 2022 Paper 2, Question 3(a): Show each step of a merge sort on eight numbers 3 marks
The specification is AQA's own document; this page says which of our lessons teach point 3.1.2 and is not endorsed by the board.