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Author Topic: Bubblesort  (Read 2410 times)

Beachtante

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Bubblesort
« on: June 20, 2018, 07:02:41 pm »
Code: Pascal  [Select]
  1. procedure  Tauschen(var a,b: integer );
  2.  
  3.  Var   Ztemp : Integer;
  4.  
  5.  begin                                              //Tausch Prozedur für den Sortieralgorithmus
  6.        ztemp :=  a;
  7.        a     :=  b;
  8.        b     := ztemp;
  9.  
  10.  end;
  11. procedure TFrm_Bubblesort.Btn_SortierenClick(Sender: TObject);
  12.  
  13. var       neul,i,limit : integer;
  14.  
  15.  
  16. begin
  17.      Mmo_sort.lines.clear;
  18.        limit:= high( zahlen );
  19.  
  20.          repeat
  21.          neul:=0;
  22.          for i := 1 to limit do
  23.          begin
  24.            if zahlen[ i-1 ] < zahlen[i] then
  25.               begin
  26.                    Tauschen(zahlen[i-1], zahlen[i]);
  27.                    neul := i;
  28.  
  29.               end;
  30.  
  31.            end;
  32.          Mmo_sort.lines.add(IntToStr(zahlen[i]));
  33.          limit:=Neul;
  34.          until limit=0 ;
  35.  
  36. end;
  37.  
Hey there !
Ive got the fowllowing problem. I have to make a programm( in school ) wich sorts numbers in the algorithm of Bubblesort.
I already got almost everything done. But in the output it doesnt show mostly the first and the last number.
My teacher said that the problem is hanging somewhere in the index. But now im at the point that i cant do it by myself.
Because i am sitting at this already about like 4-6 houers to get this done.
So if somebody have time to help me .I would be very Thankfull.

ps the code is attached and the
names are in german so if dont know something then ask.
Thats because im from germany so that would excuse my english  :D.   
« Last Edit: June 20, 2018, 07:43:44 pm by Beachtante »

Bart

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Re: Bubblesort
« Reply #1 on: June 20, 2018, 07:21:56 pm »
Please simply put the code inside [ code ] [ /code ] tags (without the spaces, I put them there to fool de forum software). You can use the button with # on it, right above the field where you type your message.

Bart

lainz

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Re: Bubblesort
« Reply #2 on: June 20, 2018, 07:28:35 pm »
Too much time from the first bubblesort I wrote =)

If there's a problem about a lost item, check the boundaries or indexes..

Munair

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Re: Bubblesort
« Reply #3 on: June 20, 2018, 07:29:42 pm »
In your first condition it should be i - 1 instead of i + 1. Same goes for the swap. Have a look at this wiki for a good example: http://wiki.freepascal.org/Bubble_sort It seems you're almost there.
« Last Edit: June 20, 2018, 07:32:02 pm by Munair »
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Beachtante

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Re: Bubblesort
« Reply #4 on: June 20, 2018, 07:34:16 pm »
In your first condition it should be i - 1 instead of i + 1. Same goes for the swap. Have a look at this wiki for a good example: http://wiki.freepascal.org/Bubble_sort It seems you're almost there.

I changed now but i didnt fixed my problem at all, it didnt show the last to numbers.
« Last Edit: June 20, 2018, 07:37:00 pm by Beachtante »

Beachtante

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Re: Bubblesort
« Reply #5 on: June 20, 2018, 07:35:48 pm »
Too much time from the first bubblesort I wrote =)

If there's a problem about a lost item, check the boundaries or indexes..

i checked them but i dont know if its right or false xD because I am not an expert im a beginner i only know basics

Beachtante

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Re: Bubblesort
« Reply #6 on: June 20, 2018, 07:36:13 pm »
Please simply put the code inside [ code ] [ /code ] tags (without the spaces, I put them there to fool de forum software). You can use the button with # on it, right above the field where you type your message.

Bart

Thanks for the information

Bart

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Re: Bubblesort
« Reply #7 on: June 20, 2018, 07:37:24 pm »
Code: Pascal  [Select]
  1.   if zahlen[ i+1 ] < zahlen[i]

What happens if i = limit?
You then access zahlen[limit+1].
I don't think you want to do that.

Bart

Beachtante

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Re: Bubblesort
« Reply #8 on: June 20, 2018, 07:42:43 pm »
Code: Pascal  [Select]
  1.   if zahlen[ i+1 ] < zahlen[i]

What happens if i = limit?
You then access zahlen[limit+1].
I don't think you want to do that.

Bart

 idk what you mean, ive got it already changed

Bart

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Re: Bubblesort
« Reply #9 on: June 20, 2018, 07:43:50 pm »
Give an array with boundaries Low..High you basically do

Code: Pascal  [Select]
  1. repeat
  2.   for i := Low to High-1 do
  3.   begin
  4.     set some flag that indicates a swap was needed to false
  5.     if array[i] > array[i+1] then swap these and set the flag that a swap was needed to true
  6.   end;
  7. until no swap was needed

Unrelated:
I would suggest to make the procedure that swaps a nested procedure of the sorting procedure and make the parameter indices to the array.
That will make your teacher happy.

Bart

Munair

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Re: Bubblesort
« Reply #10 on: June 20, 2018, 07:48:43 pm »
Take a good look at the example I gave you. There is another error in your code.
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Thaddy

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Re: Bubblesort
« Reply #11 on: June 20, 2018, 08:28:46 pm »
Take a good look at the example I gave you. There is another error in your code.
Maybe this helps to obfuscate < 8) >
Code: Pascal  [Select]
  1. program champagnesort;
  2. {$mode objfpc}
  3. function BubblesSort(var a: array of integer ):boolean;
  4. var
  5.   finished, i:integer;
  6. begin
  7.   Result := High( a ) <> 0;
  8.   repeat
  9.     finished := 0;
  10.     for i := Succ(low(a)) to High(a) do
  11.       begin
  12.         if a[ Pred(i) ] > a[ i ] then // xor swap
  13.           begin
  14.             a[Pred(i)] := a[Pred(i)] xor a[i];
  15.             a[i] := a[Pred(i)] xor a[i];
  16.             a[Pred(i)] := a[Pred(i)] xor a[i];
  17.             finished := i ;
  18.           end;
  19.       end ;
  20.   until Result = (finished = 0);
  21. end;
  22.  
  23. var
  24.   a:array of integer;
  25.   v:integer;
  26. begin
  27.   a := [123123,12,1,55,6686,5,1555,666];
  28.   Bubblessort(a);
  29.   for v in a do writeln(v);
  30. end.
Modern pascal. Adapted from our wiki. Programming with xor swap, saves temp..
« Last Edit: June 20, 2018, 08:45:18 pm by Thaddy »
inline variables like in D10.3 are a bit like Brexit: if you are given the wrong information it sounds like a good idea. Every kid loves candy, but it makes you fat and your teeth will disappear.

Bart

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Re: Bubblesort
« Reply #12 on: June 20, 2018, 08:35:06 pm »
Maybe this helps to obfuscate < 8) >

LOL

Bart

Thaddy

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Re: Bubblesort
« Reply #13 on: June 20, 2018, 08:36:45 pm »
I removed another temp. We just crossed... And made it slightly more useful in a thread (by making it a Boolean function). Rather proud of this...  8-)
If this was homework, nobody is going to believe Beachtante..... :'( Oh, and of course, it works....
« Last Edit: June 20, 2018, 08:59:38 pm by Thaddy »
inline variables like in D10.3 are a bit like Brexit: if you are given the wrong information it sounds like a good idea. Every kid loves candy, but it makes you fat and your teeth will disappear.

lainz

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