Editing Sorting algorithm (section)

== Related algorithms ==
Related problems include [[K-sorted sequence#Algorithms|approximate sorting]] (sorting a sequence to within a certain [[rank correlation|amount]] of the correct order), [[partial sorting]] (sorting only the ''k'' smallest elements of a list, or finding the ''k'' smallest elements, but unordered) and [[selection algorithm|selection]] (computing the ''k''th smallest element). These can be solved inefficiently by a total sort, but more efficient algorithms exist, often derived by generalizing a sorting algorithm. The most notable example is [[quickselect]], which is related to [[quicksort]]. Conversely, some sorting algorithms can be derived by repeated application of a selection algorithm; quicksort and quickselect can be seen as the same pivoting move, differing only in whether one recurses on both sides (quicksort, [[divide-and-conquer algorithm|divide-and-conquer]]) or one side (quickselect, [[decrease-and-conquer]]).

A kind of opposite of a sorting algorithm is a [[shuffling algorithm]]. These are fundamentally different because they require a source of random numbers. Shuffling can also be implemented by a sorting algorithm, namely by a random sort: assigning a random number to each element of the list and then sorting based on the random numbers. This is generally not done in practice, however, and there is a well-known simple and efficient algorithm for shuffling: the [[Fisher–Yates shuffle]].

Sorting algorithms are ineffective for finding an order in many situations. Usually, when elements have no reliable comparison function (crowdsourced preferences like [[voting systems]]), comparisons are very costly ([[group tournament ranking system|sports]]), or when it would be impossible to pairwise compare all elements for all criteria ([[ranking (information retrieval)|search engines]]). In these cases, the problem is usually referred to as ''ranking'' and the goal is to find the "best" result for some criteria according to probabilities inferred from comparisons or rankings. A common example is in chess, where players are ranked with the [[Elo rating system]], and rankings are determined by a [[:Category:Tournament systems|tournament system]] instead of a sorting algorithm.