Chapter 7, Problem 17E

Modified method definition for “selectionSort” method in Listing 7.10:

The modified method definition for “selectionSort” is given below:

/* Method definition for sorting the array using selection sort */

public static void selectionSort(int[] anArray, int first, int last)

{

/* Check the condition using "while" loop. The loop will perform up to "first <= last" */

    while(first <= last)

    {

/* Put the exact value in anArray[index]. Call the method "getIndexOfSmallest" with argument "first" and "anArray" and store the result into "indexOfNextSmallest" */          

int indexOfNextSmallest = getIndexOfSmallest(first, anArray);

/* Call the method "interchange" with given three arguments */

interchange(first, indexOfNextSmallest, anArray);

        /* Increment index of "first" */

        first++;

    }

}

Explanation:

The above method “selectionSort” is used to sort an array whose indices range from “first” to “last”.

• • The method “selectionSort” contains three arguments “anArray”, “first” and “last”.
  • ○ First check the condition using “while” loop. This loop performs up to “first <= last”.
    • ■ Put the exact value in “anArray[index]”. Call the method “getIndexOfSmallest” with argument “first” and “anArray” and store the result into “indexOfNextSmallest”.
    • ■ Call the method “interchange” with given three arguments.
    • ■ Increment the index value of “first”.

Complete program:

The complete executable code for after modifying the “selectionSort” method of class “ArraySorter” in Listing 7.10 is given below:

Modified “ArraySorter.java”

/* Define "ArraySorter" class */

public class ArraySorter

{

/* Method definition for sorting the array using selection sort */

public static void selectionSort(int[] anArray, int first, int last)

    {

/* Check the condition using "while" loop. The loop will perform up to "first <= last" */

        while(first <= last)

        {

/* Put the exact value in anArray[index]. Call the method "getIndexOfSmallest" with argument "first" and "anArray" and store the result into "indexOfNextSmallest" */         

int indexOfNextSmallest = getIndexOfSmallest(first, anArray);

/* Call the method "interchange" with given three arguments */

interchange(first, indexOfNextSmallest, anArray);

            /* Increment index of "first" */

            first++;

        }

    }

/** Returns the index of the smallest value in the portion of the array that begins at the element whose index is startIndex and ends at the last element. */

/* Method definition for gets index of smallest element */

private static int getIndexOfSmallest(int startIndex, int[] a)

    {

        /* Assign minimum value */

        int min = a[startIndex];

        /* Assign index of minimum value */

        int indexOfMin = startIndex;

/* Compute the index of minimum value using "for" loop */

for (int index = startIndex + 1; index < a.length; index++)

        {

            if (a[index] < min)

            {

                min = a[index];

                indexOfMin = index;

// Assertion: min is smallest of a[startIndex] through a[index]

            }

        }

        /* Return index of minimum element */

        return indexOfMin;

    }

/** Precondition: i and j are valid indices for the array a...