Sorting Algorithms: Bubble Sort, Merge Sort, and Insertion Sort

Sorting algorithms arrange data into a specific order — usually ascending (smallest to largest) or descending (largest to smallest). In GCSE Computer Science, you must understand three sorting algorithms: bubble sort, merge sort, and insertion sort. You need to know how each works, trace through examples, and compare their efficiency.

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Bubble Sort

Bubble sort works by repeatedly comparing adjacent pairs of items and swapping them if they are in the wrong order. The largest unsorted value "bubbles" to the end of the list after each pass. The algorithm repeats until no swaps are made in a complete pass.

How Bubble Sort Works

1. Start at the beginning of the list
2. Compare the first two adjacent items
3. If they are in the wrong order, swap them
4. Move to the next pair and repeat
5. After one complete pass, the largest item is in its correct position
6. Repeat the process for the remaining unsorted items
7. Stop when a complete pass is made with no swaps (the list is sorted)

Pseudocode for Bubble Sort