An example of the choice sorting algorithm for Java array implementation _java

I. Algorithm description
Select sort: For example, in a unordered array of length n, the first pass through n data, find the smallest of the number and the first element of the exchange, the second traversal of the remaining N-1 data, find the smallest of the number and the second element exchange ... The N-1 trip traverses the remaining 2 data and finds the smallest number in exchange for the first N-1 element, which is done by selecting the order.
Take the following 5 unordered data as an example:
56 12 80 91 20 (this article only refines the first selection process)
1th Trip: 12 56 80 91 20

2nd Trip: 12 20 80 91 56
3rd Trip: 12 20 56 91 80
4th Trip: 12 20 56 80 91
two. Algorithm analysis
Average Time complexity: O (n2)
Space complexity: O (1) (for Exchange and recording index)
Stability: Instability (such as sequence "5, 5, 3" The first trip will be the first [5] and [3] exchange, causing the first 5 to move to the second 5 back)
three. Algorithm implementation

 
public class Selectionsort {public static void main (string[] args) {int len = 15; 
    int[] ary = new Int[len]; 
    Random Random = new Random (); 
    for (int j = 0; J < Len; J +) {Ary[j] = random.nextint (1000); 
} System.out.println ("Before-------------sort"); Ary=new int[]{10,9,8,7,6,5,4,3,2,1}; Test Exchange times//Ary=new int[]{1,2,3,4,5,6,7,8,10,9}; 
    The number of test exchanges for (int j = 0; J < Ary.length J + +) {System.out.print (Ary[j] + ""); 
    } selectdesc (ary); 
  SELECTASC (ary); /* * Select Sort: Descending */static void Selectdesc (int[] ary) {int comparecount = 0;//compare times int Changecount 
    = 0;//exchange number int len = ary.length; int maxvalueindex =-1;  Record a comparison of the minimum index for (int i = 0; i < len-1 i++) {maxvalueindex = i;//starting from 0 for (int j = i + 1; j < Len; 
        J + +) {if (Ary[maxvalueindex] < ary[j]) {maxvalueindex = J;//record large index comparecount++; 
     } }//System.out.println ("minvalueindex==" + maxvalueindex); if (Maxvalueindex!= i) {//If the record index to the left is different, swap ary[i] = Ary[maxvalueindex] + (Ary[maxvalueindex] = ary[i]) * 0;//one step 
      Change changecount++; 
    } System.out.println ("\ n-------Descending sort------compare times:" + Comparecount + ", number of exchanges + Changecount); 
    for (int j = 0; J < Ary.length J + +) {System.out.print (Ary[j] + ""); 
    }/* * Select sort: ascending/static void Selectasc (int[] ary) {int comparecount = 0, changecount = 0; 
    int len = ary.length; 
    int minindex =-1; 
      for (int i = 0; i < len-1 i++) {minindex = i; 
          for (int j = i + 1; j < Len; J + +) {if (Ary[minindex] > Ary[j]) {minindex = J;//record smaller index 
        comparecount++; 
        } if (Minindex!= i) {//If the record index to the left is different, swap ary[i] = Ary[minindex] + (Ary[minindex] = ary[i]) * 0; 
      changecount++; }} SYSTEM.OUT.PRintln ("\ n-------Ascending sort------Compare times:" + Comparecount + ", exchange times" + Changecount); 
    for (int j = 0; J < Ary.length J + +) {System.out.print (Ary[j] + ""); 

 } 
  } 
}

Print

-------Sort before------ 
648 789 319 699 855 755 552 489 187 916 596 731 852  
-------Descending sort------compare times: 26, number 
of exchanges 916 855 852 789 755 731 699 648 596 552 489 319 187  
-------Ascending sort------compared number of times: 56, Exchange 7 
125 187 319 350 489 2 596 648 699 731 755 789 852 855 916