Thread: Selection sort code needs reverse

Hi, I've been working on this part of the code for at least 10 hours.

private static void  selectionSort( int[]  arr )
	{				
		for (int stopInd = arr.length - 1; stopInd >= 0; stopInd--) {
			int positionOfMax = indOfMax(arr,stopInd);
			for (int i = 0; i <= stopInd; i++) {
				if (arr[i] < arr[positionOfMax])
					positionOfMax = i;
 
			}
			int temp = arr[stopInd];  // swap stopInd item with biggest item
			arr[stopInd] = arr[positionOfMax ];
			arr[positionOfMax] = temp;
		}
	}

It finally works but there's a slight problem: The selection sort sorts from larges => smallest.

I.e.

RANDOM:
127 16 175 114 64 5 169 80 53 122 126 82 103 197 195 150 177 161 154 164
SELECTIONSORTED:
197 195 177 175 169 164 161 154 150 127 126 122 114 103 82 80 64 53 16 5

But i want it to be 5, 16, 56, 64 etc.

I've switched THE if (arr[i] < arr[positionOfMax]) "<" TO ">" but it doesn't work. instead i would get:

RANDOM:
34 119 56 40 83 11 190 168 138 154 63 163 33 141 39 71 99 21 172 18
SELECTIONSORTED:
190 34 119 56 40 83 11 18 168 138 154 63 163 33 141 39 71 99 21 172

And the program we're writing using cmd line args and I can't find a way to use debugging mode(looking at each step of line of code) on eclipse with cmd line args becaues it just executes at once.

Full code

/*
  Program2.java
 
 
 
*/
 
 
import java.io.*;
import java.util.*;
 
 
public class Program2
{
	private static final int NOT_FOUND = -1;
 
    public static void main( String[] args )
    {
 
try // ILL EXPLAIN THIS IN CLASS SOON. JUST LEAVE IT IN HERE SO YOUR PROGRAM CRASH CANT CRASH THE GRADING SCRIPT
	{
 
 
        Random rand = new Random();
		int[] arr;
 
        if (args.length < 1 )
        {
            System.out.println("\n\n      !! You must enter a desired arr length on the cmd line !!\n");
            System.exit(0);
        }
 
        int dimension = Integer.parseInt(args[0]);
 
		if ( dimension < 100 && dimension > 10)
		{// YOU MUST VALIDATE THAT 10 < DIMENSION < 100.  JUST EXIT IF INVALID
 
		arr = new int[dimension];
 
		randomizearr( arr ); // fill with random ints between 1 .. dimension*10 inclusive
		printarr( "\nRANDOM:", arr );
		bubbleSort( arr );
		printarr( "BUBBLESORTED:", arr );
 
		randomizearr( arr );  // fill with random ints between 1 .. dimension inclusive
		printarr( "RANDOM:", arr );
		selectionSort( arr );
		printarr( "SELECTIONSORTED:", arr );
 
 
		}
		else {
			System.out.println("Invalid. Program now exits.");
		}
 
	} // LEAVE THIS HERE - DO NOT MODIFY
	catch (Exception e ) // catch-all  Exception is the most general Exception type
	{
		System.out.println("EXCEPTION DETECTED\n" + e );  // THIS WILL SHOW UP IN YOUR OUTPUT AND I CAN DETECT IT
		System.exit(0);
	}
 
	} // END MAIN
 
	// ########################################################################################
// - - - - - - - - -  Y O U  A R E    G I V E N    T H E S E   M E T H O D S.  D O  N O T   M O D I F Y   - - - - - - - - - - -
 
    // USE THIS METHOD AS GIVEN: DO NOT CHANGE
 
    private static void printarr( String label, int[] arr )
    {
        System.out.println(label);
        for( int i=0 ; i<arr.length ;++i )
            System.out.printf("%-3d ",arr[i] );
        System.out.println();
    }
 
 
 
    // USE THIS METHOD AS GIVEN: DO NOT CHANGE
 
	private static void randomizearr( int[] arr )
	{
		Random r = new  Random();
		int i=0;
		while ( i < arr.length  )
		{
			int n = r.nextInt(arr.length*10) + 1;  // 1 .. dimension*10 inclusive
 
			// INSERT ONLY IF NUMBER NOT ALREADY IN arr
 
			if (  linearSearch( arr, n ) == -1  ) arr[i++] = n;
		}
	}
 
 
 	// USE THIS METHOD AS GIVEN: DO NOT CHANGE
 
	private static int linearSearch( int[] arr, int target )
	{
		for ( int i=0 ; i < arr.length ; ++ i )
			if (arr[i] == target ) return i;
 
		return NOT_FOUND; // i.e. return -1 which is never a valid index - means NOT_FOUND
	}
 
 
 
 
 
 
 
 
 
 
// - - - - - - - - -  Y O U   W R I T E   T H E S E   M E T H O D S   B E L O W - - - - - - - - - - -
 
 
	// YOU  WRITE THIS METHOD
	// BUBBLESORT:
	private static void bubbleSort( int[] arr )
	{
	      boolean swapped = true;
	      int j = 0;
	      int temp;
	      while (swapped) {
	            swapped = false;
	            j++;
	            for (int i = arr.length-2; i >= 0 ; i--) {                                       
	                  if (arr[i] > arr[i + 1]) {                          
	                        temp = arr[i];
	                        arr[i] = arr[i + 1];
	                        arr[i + 1] = temp;
	                        swapped = true;
	                  }
	            }                
	      }
 
		// YOUR CODE HERE
 
		//	for i= index of the next_to_last element  DOWNTO 0
		//			for j = 0 upto i
		//					if arr[j] and arr[j+1] are out of order then swap 'em
 
	}
 
 
	// YOU  WRITE THIS METHOD
	// SELECTIONSORT
	private static void  selectionSort( int[]  arr )
	{				
		for (int stopInd = arr.length - 1; stopInd >= 0; stopInd--) {
			int positionOfMax = indOfMax(arr,stopInd);
			for (int i = 0; i <= stopInd; i++) {
				if (arr[i] < arr[positionOfMax])
					positionOfMax = i;
 
			}
			int temp = arr[stopInd];  // swap stopInd item with biggest item
			arr[stopInd] = arr[positionOfMax ];
			arr[positionOfMax] = temp;
		}
	}
 
	// YOU  WRITE THIS METHOD
	// INDOFMAX
	// WITH EACH CALL FROm SELECTION SORT YOU WILL BE PASSING  IN THE RIGHT SIDE SstopIndPING POINT
	//	OF HOW FAR INTO THE arr TO SCAN
	// ONLY SCAN THAT SUB-RANGE AND RETURN THE INDEX OF THE LARGEST ELEMENT IN THE SUB-RANGE
	private static int indOfMax( int[] arr,  int stopIndInd )
	{
		// YOUR CODE HERE
		// for i = 0 upto index of last element
		//		keep track of the largest number you have seen so far and save the index postion of each new winner
		//
		// return the index position of the largest numnber seen
		int max = arr[0];
		for(int i = 1; i < arr.length; i++){
			if(arr[i] > max) {
				max = arr[i];
				stopIndInd = i;
			}
		}
 
return stopIndInd;  // JUST TO MAKE IT COMPILE - YOU CHANGE AS NEEDED
	}
 
 
} // END Of CLASS PROGRAM2

Help will be appreciated