Question

Another simple sort is the odd-even sort. The idea is to repeatedly make two
passes through the array. On the first pass you look at all the pairs of items,
a[j] and a[j+1], where j is odd (j = 1, 3, 5, …). If their key values are out of
order, you swap them. On the second pass you do the same for all the even
values (j = 2, 4, 6, …). You do these two passes repeatedly until the array is
sorted. Replace the bubbleSort() method in bubbleSort.java (Listing 3.1) with
an oddEvenSort() method. Make sure it works for varying amounts of data.
You’ll need to figure out how many times to do the two passes.

LISTING 3.1 The bubbleSort.java Program
// bubbleSort.java
// demonstrates bubble sort
// to run this program: C>java BubbleSortApp
////////////////////////////////////////////////////////////////
class ArrayBub
{
private long[] a; // ref to array a
private int nElems; // number of data items
//--------------------------------------------------------------
public ArrayBub(int max) // constructor
{
a = new long[max]; // create the array
nElems = 0; // no items yet
}
//--------------------------------------------------------------
public void insert(long value) // put element into array
{
a[nElems] = value; // insert it
nElems++; // increment size
}
//--------------------------------------------------------------
public void display() // displays array contents
{
for(int j=0; j<nElems; j++) // for each element,
System.out.print(a[j] + “ “); // display it
System.out.println(“”);
}
//--------------------------------------------------------------
public void bubbleSort()
Bubble Sort 85
{
int out, in;
for(out=nElems-1; out>1; out--) // outer loop (backward)
for(in=0; in<out; in++) // inner loop (forward)
if( a[in] > a[in+1] ) // out of order?
swap(in, in+1); // swap them
} // end bubbleSort()
//--------------------------------------------------------------
private void swap(int one, int two)
{
long temp = a[one];
a[one] = a[two];
a[two] = temp;
}
//--------------------------------------------------------------
} // end class ArrayBub
////////////////////////////////////////////////////////////////
class BubbleSortApp
{
public static void main(String[] args)
{
int maxSize = 100; // array size
ArrayBub arr; // reference to array
arr = new ArrayBub(maxSize); // create the array
arr.insert(77); // insert 10 items
arr.insert(99);
arr.insert(44);
arr.insert(55);
arr.insert(22);
arr.insert(88);
arr.insert(11);
arr.insert(00);
arr.insert(66);
arr.insert(33);
arr.display(); // display items
arr.bubbleSort(); // bubble sort them
86 CHAPTER 3 Simple Sorting
LISTING 3.1 Continued
arr.display(); // display them again
} // end main()
} // end class BubbleSortApp
////////////////////////////////////////////////////////////////

The main() routine inserts 10 items into the array in random order, displays the
array, calls bubbleSort() to sort it, and then displays it again. Here’s the output:
77 99 44 55 22 88 11 0 66 33
0 11 22 33 44 55 66 77 88 99

Answer 1

import java .util.*;
class ArrayBub
{
private long[] a; // ref to array a
private int nElems; // number of data items
//--------------------------------------------------------------

public ArrayBub(int max) // constructor
{
    a = new long[max]; // create the array
    nElems = 0; // no items yet
}

//--------------------------------------------------------------
public void insert(long value) // put element into array
{
    a[nElems] = value; // insert it
    nElems++; // increment size
}
//--------------------------------------------------------------

public void display() // displays array contents
{
    for(int j=0; j<nElems; j++) // for each element,
        System.out.print(a[j] + " "); // display it
    System.out.println();
}
//--------------------------------------------------------------

//oddEveNSort..................................................
public void oddEvenSort()
{
boolean isSorted = false; // Initially array is unsorted
        int passes=0;
        while (!isSorted)
        {
            isSorted = true;
          

            // Perform Bubble sort on odd indexed element
            for (int i=1; i<=nElems-2; i=i+2)
            {
                if (a[i] > a[i+1])
                {
                  
                   swap(i,i+1);
                   passes++;
                    isSorted = false;
                }
            }

            // Perform Bubble sort on even indexed element
            for (int i=0; i<=nElems-2; i=i+2)
            {
                if (a[i] > a[i+1])
                {
                    swap(i,i+1);
                    passes++;
                    isSorted = false;
                }     
           }
        }

    System.out.printf("Number of times passes occurs: %d ", passes);
    System.out.println();
  

}// end oddEvenSort()

//--------------------------------------------------------------
private void swap(int one, int two)
{
    long temp = a[one];
    a[one] = a[two];
    a[two] = temp;
}

//--------------------------------------------------------------
} // end class ArrayBub

////////////////////////////////////////////////////////////////
class BubbleSortApp

{
    public static void main(String[] args)
    {
    int maxSize = 100; // array size
    ArrayBub arr; // reference to array
    arr = new ArrayBub(maxSize); // create the array
    arr.insert(77); // insert 10 items
    arr.insert(99);
    arr.insert(44);
    arr.insert(55);
    arr.insert(22);
    arr.insert(88);
    arr.insert(11);
    arr.insert(00);
    arr.insert(66);
    arr.insert(33);
    arr.display(); // display items
    arr.oddEvenSort(); // bubble sort them
    arr.display(); // display them again
    } // end main()
} // end class BubbleSortApp

Code

1 import java .util.; 2 class ArrayBub 4 private long[] a; // ref to arraya 5 private int nElems; // number of data items 7 8 public ArrayBub(int max) // constructor 9 a -new long[max]; // create the array nElemse; /7 no items yet 10 15 public void insert(long value) //put element into array 16 17 18 19 a[nElems]value; // insert it nElems++;// increment size 21 23 public void display()// displays array contents 25 26 27 28 for(int j-e; j<nElems; j++)//for each element, System.out.print(alj] "); / display it System .out.println);

33 public void oddEvenSort() 35 boolean issorted false;// Initially array is unsorted int passes- while (!isSorted) 37 38- 39 40 41 42 43 44- 45 46 47 48 49 isSorted true; /Perform Bubble sort on odd indexed element for (int i-1; i(snElems-2; ii+2) swap (i,i+1); passes++ isSorted false; 51 52 53 54 /Perform Bubble sort on even indexed element for (int i-0; i<-nElems-2; i-i+2) 57 59 60 61 62 63 64 swap(i,i+1); passes++ isSorted false;

arr.insert (22); arr.insert (88); arr.insert (11); arr.insert (00); arr.insert (66); arr.insert (33); arr.display) // display items arr.oddEvenSort(); // bubble sort thenm arr.display) // display them again // end main() 98 100 101 102 103 184 105 106 107 108 109 // end class BubbleSortApp

Output

77 99 44 55 22 88 11 0 66 33 Number of times passes occurs: 31 0 11 22 33 44 55 66 77 88 99