Problem Solving with Algorithms and Data Structures using C++ The PreTeXt Interactive Edition

A bubble sort, a selection sort, and an insertion sort are $O(n^2)$ algorithms.

A shell sort improves on the insertion sort by sorting incremental sublists. It falls between $O(n)$ and $O(n^2)\text{.}$

A merge sort is $O(n\log n)\text{,}$ but requires additional space for the merging process.

A quick sort is $O(n\log n)\text{,}$ but may degrade to $O(n^2)$ if the split points are not near the middle of the list. It does not require additional space.