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Gambet
10-11-2008, 10:00 AM
A little over a year ago I released an example of how to use the Bubble Sort algorithm to sort a set of data, which can be found here (http://forums.graalonline.com/forums/showthread.php?t=71349).

I started my Freshman year at my University in the Fall, and for the Programming I course we're learning OOP via Java (going to be a CS Major). The sorting algorithm that we were taught was the Selection Sort method, which is more efficient than the Bubble Sort method; and considering the fact that I posted the Bubble Sort method, it only fits that I show you the Selection Sort method as well.

I programmed it in Java since it's the only thing that I could use at the moment to test the code, but the method itself is the same regardless of the language so it shouldn't be a problem to understand how to convert it to GScript for whomever might use it.


SelectionSort.java:


/*
*@author Gambet
*/

public class SelectionSort
{
double dataSet[] = {1, 6, 4, 2, 5, 8, 20, 100, 54, 1000, 523};

public void selectionSort()
{
for (int a = 0; a < dataSet.length-1; a++)
{
for (int b = a+1; b < dataSet.length; b++)
{
if (dataSet[b] < dataSet[a])
{
double results = dataSet[b];
dataSet[b] = dataSet[a];
dataSet[a] = results;
}
}
}
}

public void showResults()
{
for(int sorted = 0; sorted < dataSet.length; sorted++)
{
System.out.println(dataSet[sorted]);
}
}
}



TestSelectionSort.java:


class TestSelectionSort
{
public static void main(String[] args)
{
SelectionSort s = new SelectionSort();
s.selectionSort();
s.showResults();
}
}




1.0
2.0
4.0
5.0
6.0
8.0
20.0
54.0
100.0
523.0
1000.0



The above code sorts from least to greatest. To convert from greatest to least, switch:


if (dataSet[b] < dataSet[a])


to


if (dataSet[b] > dataSet[a])




NOTE: I used the same set of values that I used for the Bubble Sort algorithm.

Crono
10-11-2008, 12:59 PM
Had to do something like this last week or so, except I went the lame way and used Collections.sort(). Of course I messed up after it sorted it by 1 12 13 2 3 4. Should re-do it using your logic here, thanks. :]

xXziroXx
10-11-2008, 02:31 PM
I thought we were not allowed to post non-GScript scripts in the Code Library. :noob:

Programmer
10-11-2008, 04:25 PM
I converted it to GScript so that it can be tested by Graal developers.


dataSet = {1, 6, 4, 2, 5, 8, 20, 100, 54, 1000, 523};

echo(dataSet);
selectionSort();
echo(dataSet);

function selectionSort()
{
for (a = 0; a < dataSet.size() - 1; a++)
{
for (b = a + 1; b < dataSet.size(); b++)
{
if (dataSet[b] < dataSet[a])
{
result = dataSet[b];
dataSet[b] = dataSet[a];
dataSet[a] = result;
}
}
}
}


Very nice, Gambet.

I thought we were not allowed to post non-GScript scripts in the Code Library. :noob:

I did the same thing about 2 years ago when I posted the Java code for an analog clock. Skyld let it stay for the reason that the formula might help some people, and this is a similar case.

cbk1994
10-11-2008, 06:03 PM
Very nice, I will likely end up using this somewhere.

Gambet
10-11-2008, 06:48 PM
I thought we were not allowed to post non-GScript scripts in the Code Library. :noob:


My apologizes if you can't, but I haven't played Graal in quite some time so I wouldn't have a method of testing the code since GScript is fabricated and has no standalone compiler. It's not so much that I wouldn't be able to do it in GScript myself, but I'd rather release something that I was certain was error proof rather than just writing code in some text file and assuming everything in it will compile and run.


From an educational standpoint, the importance is learning the Selection Sort algorithm so that you can apply it to any programming language.


I converted it to GScript so that it can be tested by Graal developers.



Thank you. :)

Understood
10-11-2008, 07:44 PM
Very nice, I will likely end up using this somewhere.

This is what I used for the trivia scores =p

napo_p2p
10-11-2008, 08:49 PM
A good example for new scripters :). I have a feeling that you'll be back for one of the O(n log n) algorithms.

Had to do something like this last week or so, except I went the lame way and used Collections.sort(). Of course I messed up after it sorted it by 1 12 13 2 3 4. Should re-do it using your logic here, thanks. :] If you use List<Integer>, I believe that Collections.sort() will sort numerically.

cbk1994
10-11-2008, 10:07 PM
This is what I used for the trivia scores =p

Looking over the code, that's actually pretty much what I did on Vesporia as well.

kingdom_90
10-11-2008, 10:38 PM
Good efficient code there :) Good job

Tolnaftate2004
10-11-2008, 10:52 PM
If you're looking for something even a bit more efficient, I would look up the quicksort algorithm.

Gambet
10-11-2008, 11:10 PM
If you're looking for something even a bit more efficient, I would look up the quicksort algorithm.



Yeah, that would also fall under the O(n log n) that napo addressed. I believe that the algorithms course that we have over here is an upper-division course, so I suppose I'll get into the higher-level sorting methods as I progress into the major.

napo_p2p
10-11-2008, 11:34 PM
Yeah, that would also fall under the O(n log n) that napo addressed. I believe that the algorithms course that we have over here is an upper-division course, so I suppose I'll get into the higher-level sorting methods as I progress into the major.

You might actually get to mergesort, quicksort, and heapsort sometime this year (maybe next quarter/semester), since they are not too complicated. I remember going over those in my first year.

Inverness
10-12-2008, 02:24 AM
If you need an algorithm then invoke the power of Wikipedia.

Gambet
10-12-2008, 02:24 AM
You might actually get to mergesort, quicksort, and heapsort sometime this year (maybe next quarter/semester), since they are not too complicated. I remember going over those in my first year.


Well I'm taking Programming II with Discrete Math next semester (Discrete Math being a corequisite), so it's possible. I've already read through all of the notes for my Programming I course so I know that the only sorting algorithm that we're supposed to be taught in this class is the Selection Sort method, so I simply have to look on ahead and hope the next course offers a wider range of options.

Inverness
10-12-2008, 02:32 AM
I'd suggest learning Python, its a great programming and scripting language. With Python and C++ together you can't loose.

Python is also open-source, allowing you to create C/C++ extensions for Python or embed Python into a C/C++ application which is what I'm doing.

Python Code:

def SelectionSort(array):
for a in range(len(array)):
for b in range(a + 1, len(array)):
if array[b] < array[a]:
tmp = array[b]
array[b] = array[a]
array[a] = tmp

#Testing code

data = [1, 6, 4, 2, 5, 8, 20, 100, 54, 1000, 523]
SelectionSort(data)
print(data) #Prints: [1, 2, 4, 5, 6, 8, 20, 54, 100, 523, 1000]

I converted it to GScript so that it can be tested by Graal developers.How dare you place any code outside of a function !pissed!
And you're making global variables.

Programmer
10-12-2008, 03:14 AM
How dare you place any code outside of a function !pissed!
And you're making global variables.

Zzz...


function onCreated()
{
temp.dataSet = {1, 6, 4, 2, 5, 8, 20, 100, 54, 1000, 523};

echo(temp.dataSet);
temp.dataSet = selectionSort(temp.dataSet);
echo(temp.dataSet);

temp.dataSet = null;
temp.dataSet.destroy();
}

function selectionSort(temp.data)
{
for (a = 0; a < temp.data.size() - 1; a++)
{
for (b = a + 1; b < temp.data.size(); b++)
{
if (temp.data[b] < temp.data[a])
{
result = temp.data[b];
temp.data[b] = temp.data[a];
temp.data[a] = result;
}
}
}

return temp.data;
}

Inverness
10-12-2008, 03:32 AM
Zzz...


function onCreated()
{
temp.dataSet = {1, 6, 4, 2, 5, 8, 20, 100, 54, 1000, 523};

echo(temp.dataSet);
temp.dataSet = selectionSort(temp.dataSet);
echo(temp.dataSet);

temp.dataSet = null;
temp.dataSet.destroy();
}

function selectionSort(temp.data)
{
for (a = 0; a < temp.data.size() - 1; a++)
{
for (b = a + 1; b < temp.data.size(); b++)
{
if (temp.data[b] < temp.data[a])
{
result = temp.data[b];
temp.data[b] = temp.data[a];
temp.data[a] = result;
}
}
}

return temp.data;
}

That would cause an error because temp.dataSet is not an object with a destroy() function. And temp variables are destroyed automatically anyways when the function is over, no need to set it to null. Also, function parameters are automatically temp, you don't need to specify it. It's also less costly to send the array by reference using temp.dataSet.link() rather than duplicating it. :p

function onCreated() {
temp.dataset = {1, 6, 4, 2, 5, 8, 20, 100, 54, 1000, 523};

echo(dataset);
this.selectionsort(dataset.link());
echo(dataset);
}
function selectionsort(data) {
temp.a = 0;
temp.b = 0;
temp.tmp = 0;

for (a = 0; a < data.size() - 1; a++) {
for (b = a + 1; b < data.size(); b++) {
if (data[b] < data[a]) {
tmp = data[b];
data[b] = data[a];
data[a] = tmp;
}
}
}
}

Once a temp variable is initialized it can be referenced without using the temp prefix, however using the prefix is marginally faster.

Python is superior though. :D

10-12-2008, 03:40 PM
temp.numbers = {1,4,6,2,65,20,200,4000,40,200};
for (i: temp.numbers) {
temp.e.add(i);
temp.e[temp.c].sortvalue = i;
temp.c++;
}
temp.e.sortbyvalue("sortvalue", "float", false); //Change to true for other way
for (temp.i: temp.numbers)
sendtorc(e[temp.numbers.index(i)]);

works better I suppose...?

Gambet
10-12-2008, 08:07 PM
works better I suppose...?


Nice code :)
sortascending()/sortdescending() currently only sort strings, so it's not helping in all cases. You can also use sortbyvalue() but it is more made for sorting objects


Plus, that's definitely not Selection Sort. >_<

Kristi
10-16-2008, 06:10 AM
I don't understand why they still waste time with classics like these :P The concept of hashing has pretty much crushed any algorithm that didn't use it before.

Inverness
10-16-2008, 08:07 AM
I don't understand why they still waste time with classics like these :P The concept of hashing has pretty much crushed any algorithm that didn't use it before.Maybe because smart people teach the basics before moving onto more advanced concepts.