java sorting

8/7/2019 java sorting

1/29

Introduction to SortingObjectives:

Understand the importance of sortingdata

Understand the components of a bubblesort


2/29


3/29

Vocabulary Quiz

Click back button whenfinished with quiz

Click on test icon to checkvocabulary knowledge

Follow directions given onthe web screen

Dave use the following

student to test quiz

Username: calendar

Passwprd: tercel

ap1


4/29

Slide 3

jap1 Dave use the following student to test quiz

Username: calendar

Passwprd: tercelJane , 10/4/2006


5/29

Array

An array consists of an ordered collection ofsimilar items.


6/29

Element

An element is value that is stored in anarray.


7/29

One dimensional array

An array in which each data item isaccessed by specifying a single index


8/29

Sorting

Aprogramming process which makes surevalues are in either ascending ordescending order


9/29

Bubble

Sort

A sorting algorithm that swaps consecutiveelements that are out of order to bubblethe elements to the top or bottom on each

pass of the loop.


10/29

Index

The relative position of the components of anarray. Also called a subscript.


11/29

Subscript

The relative position of the components ofan array. Also called an index.


12/29

Range bound error

The error which occurs when an attempt ismade to use an array index value that isless than 0 or greater than or equal to the

size of the array.


13/29

Array.length

This method returns the length of an arraywhich is the number of elements in the array


14/29

Sorting When the elements of an array are in random order,

we need to rearrange them before we can take

advantage of any ordering. This process is called sorting.

Suppose we have an array of five integers that we

wish to sort from smallest to largest.


15/29


16/29

BubbleSorting

Bubble Sort A bubble sort causes a pass through the

array to compare adjacent pairs of

items.

Whenever two items are out of orderwith respect to each other, they areswapped.

Click mice to see swap code

Click bubbles to see effect of swap


17/29

SwapMe

thod

public static void swap(int[] a, int x, int y){

int temp = a[x];

a[x] = a[y];

a[y] = temp;

}


18/29

Sorting

*Indicates items just compared

and swapped

Sorted item


19/29

BubbleSort

The last item will "sink" to the bottom of the array,

and preceding items will gradually bubble" to the

top.


20/29

Sorting

Next is a complete Java class to implement a

bubble sort for an array of integers


21/29

Bubble Sort Demonstration

Clickto Run


22/29

Wrap UpDiscuss the following questions with a neighbor

who is finished with the tutorial.

Be prepared to discuss these questions with the

class.


23/29

Discussion Be able to draw a diagram of what is happening

in the swap method

What is always true when one pass of the innerloop of a bubble sort is complete?

What is the purpose of the exchangeMadevariable in the bubble sort?

What one change would need to be made inorder for the array to be in descending order?


24/29


25/29

Main Sorting ProgramImport TerminalIO.*;

Public class Sort

{

public static void main(String [] args)

{

KeyboardReader reader = new KeyboardReader();

int [] numbers = new int[5]

System.out.println(This program will allow you to enter5 numbers);

System.out.println (and it will sort them in ascendingorder \n)

readNumbers(numbers[]); //click to see code

bubbleSort(numbers[]); //for each method

outputNumbers(numbers[]);

} // end sort


26/29

public static void bubbleSort(int[] numbers)

{

int k = numbers.length-1;

boolean exchangeMade = true;

// Make up to n - 1 passes through array, exit early if no exchanges

//are made on previous pass

while k > 0 && exchangeMade == true)

{exchangeMade = false;

k--;

for (int j = 0; j < k; j++)

{

if (a[j] > a[j + 1])

{swap(a, j, j + 1); //click to see swap method

exchangeMade = true;

}

} // end for

} // end while

} //end method


27/29

Input Data to be Sortedpublic static void inputNumbers(int[] numbers)

{

for (int x= 0; x < numbers.length; x++)

{

numbers{x} = reader.readInt(Please enter a number

to be sorted );

}


28/29

SwapMe

thod

public static void swap(int[] a, int x, int y){

int temp = a[x];

a[x] = a[y];

a[y] = temp;

}


29/29

utput sorted datapublic static void outputNumbers(int[] numbers)

{

System.out.println ( \nThe list in sorted order is);

for int x = 0; x < numbers.length; x++)

{

System.out.println(numbers[x]);

}

} // end method

java sorting

Documents