1. Array Review Selection Sort
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Array Review Selection Sort

2. Learning Objectives Be able to dry run programs that use arrays
Understand and be able to implement a Selection Sort.

3. Dry run 1
int[] egArray = { 2, 4, 6, 8, 10, 1, 3, 5, 7, 9 }; for ( int index= 0 ; index < 5 ; index++ ) System.out.print( egArray[ index ] + " " );

4. Dry Run 2
int[] egArray = { 2, 4, 6, 8, 10, 1, 3, 5, 7, 9 }; for ( int index= 0 ; index < egArray.length ; index++ ) System.out.print( egArray[ index ] + " " );

5. Dry Run 3
int[] egArray = { 2, 4, 6, 8, 10, 1, 3, 5, 7, 9 }; for ( int index= 0 ; index < egArray.length ; index = index + 2 ) System.out.print( egArray[ index ] + " " );

6. #4) Modify the code int[] egArray = { 2, 4, 6, 8, 10, 1, 3, 5, 7, 9 };
Fill in the blanks of the following code fragment so
that the elements of the array are printed 
in reverse order, starting with the last element.
int[] egArray = { 2, 4, 6, 8, 10, 1, 3, 5, 7, 9 };
for ( int index= ________ ; _____________ ; ______________ )
System.out.print( egArray[ index ] + " " )

7. Dry Run 5
int[] array = { 1, 4, 3, 6, 8, 2, 5}; int what = array[0]; // scan the array for ( int index=0; index < array.length; index++ ) { if ( array[ index ] > what ) what = array[ index ]; } System.out.println( what );

8. Dry Run 6
int[] array = { 1, 4, 3, 6, 8, 2, 5}; int what = array[0]; // scan the array for ( int index=0; index < array.length; index++ ) { if ( array[ index ] < what ) what = array[ index ]; } System.out.println( what );

9. Dry Run 7
int[] array = { 1, 4, 3, 6 }; int what = 0; // scan the array for ( int index=0; index < array.length; index++ ) { what = what + array[ index ] ; } System.out.println( what );

10. 8) Fill in the blank in the following code fragment so that each element of the array is assigned twice the value of its index.
int[] array = new int[10]; // scan the array for ( int index=0; index < array.length; index++ ) { _______________________ }

11. Dry Run 9
int [] list = { 10, 11, 4, 8, 2 } ;
for(int start = 1; start < list.length; start++) {
int temp = list[start];
int k = start;
while(k > 0 && list[k-1] > temp)
list[k] = list[k-1];
k--; }
list[k] = temp;
for (int s:list)
System.out.print(s +" ");
System.out.println();

12. Dry Run 10 public static void main (String [] args) {
int [] a = { 10, 11, 4, 8, 2 } ;
int out, in, min;
int dummy;
for (out=0; out<a.length-1; out++)
min = out;
for(in=out+1; in<a.length; in++)
if(a[in] < a[min] )
min = in;
dummy = a[out];
a[out] = a[min];
a[min] = dummy;
for (int s:a)
System.out.print(s +" ");
System.out.println();
} // end for(out) }

13. Selection sort How it works Example Low High 2 6 8 3 15 1 7 Stability
Stability
Speed
Your turn
High Low
Check, mark, switch
Not stable
O(n2)

14. Selection Sort //a is the array name,
// nElems = the number of elements being sorted
int out, in, min;
int dummy; // If sorting an array of ints
for(out=0; out<nElems-1; out++) // outer loop {
min = out; // minimum
for(in=out+1; in<nElems; in++) // inner loop if(a[in] < a[min] ) // Check if min greater,
min = in; // Mark, we have a new min
dummy = a[out]; //Switch
a[out] = a[min];
a[min] = dummy;
} // end for(out)

15. First Program Check for Understanding
import java.util.Scanner; // program uses class Scanner
public class SelectionSort {
public static void main(String args[])
String[] names = new String[5];
String name;
// create Scanner to obtain input from command window
Scanner input = new Scanner( System.in );
for (int count = 0 ; count < names.length; count++)
System.out.println("Please enter a name");
names[count] = input.next(); }
for (int j=0; j<names.length; j++)
System.out.println(names[j]);
//Insert Sort Code here
System.out.println("The names ...");
for (String temp: names) // For each String temp in the array names.
System.out.println(temp);
First Program Check for Understanding
Enter this into BlueJ and test to make sure it is sorting.

16. Selection Sort Program
Input 11 scores in main body
Output:
Numbers in sorted order (Low to High): Method
Mean (average): Method
Median (Middle number after sorting): Method
Push:
Find the mode: The most often occurring value. Multiple modes? No mode?
Let the user tell you how many scores prior to entering the scores
Add a method that will return an array of the 5 highest scores.
Add a method that will return the modified average.
If the pre-sorted scores are in increasing order (continual improvement), it will return the average of the top 3 scores, otherwise with will return the entire average.

17. Shell for the Selection Sort program.
import java.util.Scanner; public class SortOfFun { public static void main(String [] args) } public static void selectionSort(int [] unsortedArray) public static void show(int [] arrayToShow) public static int meany(int [] theArray) public static int medianfinder(int [] theArray)
Shell for the Selection Sort program.