Internal Sorting: Straight selection sort: Sorting by Selection

Straight selection sort:直接选择排序

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Animation

Selection sort animation

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Selection sort animation. Red is current min. Yellow is sorted list. Blue is current item.

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Complexity

Class Sorting algorithm Data structure Array Worst case performance О(n2) Best case performance О(n2) Average case performance О(n2) Worst case space complexity О(n) total, O(1) auxiliary

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Algorithm S

Algorithm S (Straight selection sort). Records R1,...,RN are rearranged in
place; after sorting is complete, their keys will be in order, K1<=...<=KN.
Sorting is based on the method indicated above, except that it proves to be
more convenient to select the largest element first, then the second largest, etc.
S1. [Loop on j.] Perform steps S2 and S3 for j=N,N−1,...,2.
S2. [Find max(K1,...,Kj).] Search through keys Kj,Kj−1,...,K1 to find a
maximal one; let it be Ki, where i is as large as possible.
S3. [Exchange with Rj.] Interchange records Ri↔Rj. (Now records Rj,...,RN
are in their final position.) |

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Flow diagram

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Data table

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Jave program

In this program, R1,…,RN were simplified to K1,…,KN.

/** * Created with IntelliJ IDEA. * User: 1O1O * Date: 12/1/13 * Time: 10:01 PM * :)~ * Straight selection sort:Sorting by Selection:Internal Sorting */public class Main {    public static void main(String[] args) {        int N = 16;        int[] K = new int[17];        int temp;        int maxIndex;        /*Prepare the data*/        K[1] = 503;        K[2] = 87;        K[3] = 512;        K[4] = 61;        K[5] = 908;        K[6] = 170;        K[7] = 897;        K[8] = 275;        K[9] = 653;        K[10] = 426;        K[11] = 154;        K[12] = 509;        K[13] = 612;        K[14] = 677;        K[15] = 765;        K[16] = 703;        /*Output unsorted Ks*/        System.out.println("Unsorted Ks:");        for(int i=1; i<=N; i++){            System.out.println(i+":"+K[i]);        }        System.out.println();        /*Kernel of the Algorithm!*/        for(int j=N; j>=2; j--){            maxIndex = j;            for(int i=1; i<=j; i++){                if(K[i] > K[maxIndex]){                    maxIndex = i;                }            }            temp = K[j];            K[j] = K[maxIndex];            K[maxIndex] = temp;        }        /*Output sorted Ks*/        System.out.println("Sorted Ks:");        for(int i=1; i<=N; i++){            System.out.println(i+":"+K[i]);        }    }}

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Outputs

Unsorted Ks:1:5032:873:5124:615:9086:1707:8978:2759:65310:42611:15412:50913:61214:67715:76516:703Sorted Ks:1:612:873:1544:1705:2756:4267:5038:5099:51210:61211:65312:67713:70314:76515:89716:908

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Reference

<< The art of computer programming: Sorting and Searching >> VOLUME 3, DONALD E. KNUTH
https://en.wikipedia.org/wiki/Selection_sort