Selection sort: Difference between revisions

Revision as of 11:08, 28 November 2024

Latest revision as of 11:10, 21 May 2025

(8 intermediate revisions by 8 users not shown)

Line 28:

|-

| ()

| style="text-align:right;" | (1112, 25, 1264, 2211, 6422)

| 11

|-

| (11)

| style="text-align:right;" | (25, 1264, 2212, 6422)

| 12

|-

| (11, 12)

| style="text-align:right;" | (2564, 2225, 6422)

| 22

|-

| (11, 12, 22)

| style="text-align:right;" | (25, 64)

| 25

|-

| (11, 12, 22, 25)

| style="text-align:right;" | (64)

| 64

|-

| (11, 12, 22, 25, 64)

| style="text-align:right;" | ()

|

|}

Line 138:

== Variants ==

[[Heapsort]] has been described as "nothing but an implementation of selection sort using the right [[data structure]]."<ref>{{cite book |first=Steven |last=Skiena |author-link=Steven Skiena |title=The Algorithm Design Manual |edition=3rd |publisher=Springer |year=2008 |page=116 |chapter=Searching and Sorting |isbn=978-3-030-54255-9 |quote=The name typically given to this algorithm, ''heapsort'', obscures the fact that the algorithm is nothing but an implementation of selection sort using the right data structure. |doi=10.1007/978-3-030-54256-6_4}}<!--DOI for chapter--></ref> It greatly improves the basic algorithm by using an [[implicit data structure|implicit]] [[heap (data structure)|heap]] [[data structure]] to speed up findingfind and removingremove the lowest datum. If implemented correctly, the heap will allow finding the nexteach lowest element in <math>\Theta(\log n)</math> time, instead of normal selection sort's <math>\Theta(n)</math> for the inner loop in normal selection sort, reducing the total running time to <math>\Theta(n\log n)</math>.

A bidirectional variant of selection sort (called '''double selection sort''' or sometimes '''cocktail sort''' due to its similarity to [[cocktail shaker sort]]) finds ''both'' the minimum and maximum values in the list in every pass. This requires three comparisons per two items (a pair of elements is compared, then the greater is compared to the maximum and the lesser is compared to the minimum) rather than regular selection sort's one comparison per item, but requires only half as many passes, a net 25% savings.

Line 154:

last := length(A) - 1;

{ The first iteration is written to look very similar to
the subsequent ones, but without swaps. }

but without swaps. }

nextMax := A[last];

for i := last - 1 downto 0 do

Line 164:

while last > 0 do begin

{ Each main loop searches for the new nextMax while

swapping items equal to prevMax into place. }

prevMax := nextMax;

nextMax := A[last];

Line 189 ⟶ 191:

== See also ==

* [[Selection algorithm]]

* [https://coseries.com/selection-sort-algorithm/ Selection sort in java]

== References ==