SINGLE-DIMENSIONAL ARRAYS - Introduction to Java Programming: Comprehensive Version - page 270

The solution can be described as follows:

for (int i = 0; i < list.length - 1; i++) {
select the smallest element in list[i..list.length-1];
swap the smallest with list[i], if necessary;
// list[i] is in its correct position.
// The next iteration applies on list[i+1..list.length-1]
}

Listing 7.8 implements the solution.

L ISTING 7.8

SelectionSort.java
1 public class SelectionSort {
2 /** The method for sorting the numbers */

3 public static void selectionSort( double [] list) {

4 for ( int i = 0 ; i < list.length - 1 ; i++) {

5 // Find the minimum in the list[i..list.length-1]

6 double currentMin = list[i];

7 int currentMinIndex = i;

8
9 for ( int j = i + 1 ; j < list.length; j++) {
10 if (currentMin > list[j]) {
11 currentMin = list[j];
12 currentMinIndex = j;
13 }
14 }
15
16 // Swap list[i] with list[currentMinIndex] if necessary
17 if (currentMinIndex != i) {
18 list[currentMinIndex] = list[i];
19 list[i] = currentMin;
20 }
21 }
22 }
23 }

select

swap

The selectionSort(double[] list) method sorts any array of double elements. The
method is implemented with a nested for loop. The outer loop (with the loop control vari-
able i ) (line 4) is iterated in order to find the smallest element in the list, which ranges from
list[i] to list[list.length-1] , and exchange it with list[i] .
The variable i is initially 0 . After each iteration of the outer loop, list[i] is in the right
place. Eventually, all the elements are put in the right place; therefore, the whole list is sorted.
To understand this method better, trace it with the following statements:

double [] list = { 1 , 9 , 4.5 , 6.6 , 5.7 , -4.5 };
SelectionSort.selectionSort(list);

7.24

✓ ✓

Use Figure 7.11 as an example to show how to apply the selection-sort approach to
sort { 3.4 , 5 , 3 , 3.5 , 2.2 , 1.9 , 2 }.

Check

Point

7.25

How do you modify the selectionSort method in Listing 7.8 to sort numbers in
decreasing order?

7.12 The Arrays Class
The java.util.Arrays class contains useful methods for common array operations
such as sorting and searching.

Key
Point