Merge sort

Computing

Algorithms

'The merge sort algorithm has two parts: splitting items and merging items'

The first part of a merge sort it to repeatedly split a list in half until all the elements are in a list by themselves.

Each stage of the merge sort algorithm can be shown in two parts: splitting the items and merging pairs of lists.

The merge sort algorithm is less complex to implement than bubble sort.

The advantage to merge sort is that it requires more memory, often due to the new lists that need to be created.

"Executing a merge sort takes up extra space in memory, as new lists are made each time a list is split or two lists are combined."

"A merge sort algorithm is usually slower to execute but more easier to write than bubble sort."

"Merge sort is an efficient divide and conquer algorithm that can perform well in real-world use."

'A more efficient version of bubble sort uses a variable to flag when a swap was made during a single pass'

'The insertion sort algorithm copies the value to be inserted in a variable at the end of each pass'

'During a pass of an insertion sort, elements in the sorted part of the list are copied into the next position, to make space for the value to be inserted'

Two improvements to the bubble sort algorithm are reducing the number of comparisons after each pass, and stopping once no swaps are made during a single pass.

"Bubble sort compares items next to each other in the list and swaps them if they are in the wrong order."

"Insertion sort compares an item from the unsorted sublist with the items in the sorted sublist and places it in the correct position."

"Bubble sort is good at sorting large collections of unordered data."

"Bubble sort can be really fast at sorting data that is nearly in order."

"Insertion sort is usually slower to execute than bubble sort on large, unordered data sets."

This lesson will be removed by end of Summer Term 2025.

Merge sort

Lesson outcome

This lesson will be removed by end of Summer Term 2025.