Merge sort is like sorting a huge pile of exam papers with friends. You split the pile in half, then split again, until everyone holds a single paper (one paper is already sorted). Then you pair up and merge the small sorted piles into bigger sorted piles, until one sorted pile is left.
Bubble sort compares neighbouring items and swaps them if they are in the wrong order, then repeats the pass. Merge sort divides the list down to single items, then merges the sorted parts back together. Insertion sort inserts each item into the sorted part. On long lists bubble sort and insertion sort make many comparisons, and merge sort makes fewer. Bubble sort and merge sort are named by OCR, AQA and Edexcel. Insertion sort is named by OCR only.
This introduction covers Split It, Sort It, Join It within Merge Sort for GCSE Computer Science. Revise Merge Sort in 3.1 Fundamentals of Algorithms for GCSE Computer Science with 16 exam-style questions and 10 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 1 of 8 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Merge Sort
Which design strategy does merge sort use?
Describe how merge sort works. You should include what happens in both the divide and merge phases.