sorting Selection Sort (Java)


Example

Animation to show how selection sort works

enter image description here

Below example shows selection sort in ascending order:

public class MySelectionSort {
 
    public static int[] doSelectionSort(int[] arr){
         
        for (int i = 0; i < arr.length - 1; i++)
        {
            int index = i;
            for (int j = i + 1; j < arr.length; j++)
                if (arr[j] < arr[index]) 
                    index = j;
      
            int smallerNumber = arr[index];  
            arr[index] = arr[i];
            arr[i] = smallerNumber;
        }
        return arr;
    }

I've written a sample main() method to show the output of the selection sort:

    public static void main(String a[]){
         
        int[] arr1 = {10,34,2,56,7,67,88,42};
        int[] arr2 = doSelectionSort(arr1);
        for(int i:arr2){
            System.out.print(i);
            System.out.print(", ");
        }
    }
}

Output of the program :

2, 7, 10, 34, 42, 56, 67, 88

Below example shows selection sort in descending order:

public static void doDescendingSelectionSort ( int [ ] num )
{
     int i, j, first, temp;  
     for ( i = num.length - 1; i > 0; i - - )  
     {
          first = 0;   //initialize to subscript of first element
          for(j = 1; j <= i; j ++)   //locate smallest element between positions 1 and i.
          {
               if( num[ j ] < num[ first ] )         
                 first = j;
          }
          temp = num[ first ];   //swap smallest found with element in position i.
          num[ first ] = num[ i ];
          num[ i ] = temp; 
      }           
}

Image Reference : Wikipedia