Need help in understanding this specific descending order selectiion sort of integers

Question

As said in title, this is a descending sort of integer using selecction sort.This is the program.. I m having difficulties in understanding the steps. Can someone help me in understanding it? Thanks in advance!!

import java.util.Scanner;
public class Selectionsort_descending
{
public static void main(String args[])
{
int i,j,k,m,n;
Scanner sc = new Scanner(System.in);
System.out.println("Enter any number");
n=sc.nextInt();
int a[]=new int [n];

for (i=0;i<=n-1;i++)
{
System.out.println("Enter number");
a[i]=sc.nextInt();
    }
for (j=0;j<=n-1;j++)
{
for (k=j;k<=n-1;k++)
{
if (a[j]<a[k])
{
m=a[j];
a[j]=a[k];
a[k]=m;
    }
}
    }
for (i=0;i<=n-1;i++)
{
System.out.print(a[i]+" ");
    }    
    }
}

Answer 1

First of all I would highly suggest to get your code more formatted. In Eclipse it is done by pressing [Ctrl]+[Shift]+[F].

By doing that, your code should look like that (I did some improvements which I will explain then).

import java.util.Scanner;

public class Selectionsort_descending {
public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter any number");
    int n = sc.nextInt();
    int a[] = new int[n];

    for (int i = 0; i < n ; i++) {
        System.out.println("Enter number");
        a[i] = sc.nextInt();
    }
    
    for (int j = 0; j < n ; j++) {
        for (int k = j; k < n; k++) {
            if (a[j] < a[k]) {
                int m = a[j];
                a[j] = a[k];
                a[k] = m;
            }
        }
    }
    
    for (int i = 0; i < n ; i++) {
        System.out.print(a[i] + " ");
    }
    
    sc.close();
}
}

Firstly I changed the "i <= n-1" to "i < n" because I think it is much more readable like this.

Secondly I declared all variables when they were actually used and not right at the beginning as you did.

In the first for-loop you enter your numbers through the console.

Then you check each number of your Array: (j for Loop)

• go through all numbers which came after this number (k for Loop)

• is the current number (a[j]) less than a number that is located later in the Array (a[k]) ? → Change positions

  This algorythm is also called "Selection Sort" if you want to read more about it. I hope i could help you!