Did the assignment require this to be done in a non-standard
way? If not, then you are over complicating a fairly simple
algorithm. Just use two nested For loops as Richard
suggested. If the assignment requires you to do it with
a while loop (though for the life of me I can't imagine
why it would) then you need make the following adjustments.
1) change your for loop to
for($j=0; $j<$tam-$i-1; $j++)
with your check being simply $tam-$i then the first time through
you compare the last element in the array with n+1 which is an
element out of the array's range. I am not sure how PHP handles
this, but if it is anything like C then it is to be avoided at all costs
(especially since there is a VERY good likelihood that you would
proceed to write to n+1). This is all moot in your script, however,
as you never actually get to the end of the array as we will see next.
2) Move $i++ OUT of your for loop. The way your script currently
reads you are not even traversing your entire array once! Lets say you
have a 4 element array...
for($j=0; $j<$tam-$i; $j++)
{
<code>
$i++
}
First time: $j=0; $i=0; $tam-$i = 4
Run loop
Second time: $j=1; $i=1 $tam-$i=3
Run Loop
Third time: $j=2; $i=2; $tam-$i=2
Continue Past Loop
So out of 4 elements, you looked at 2.
Hope that helps
Sheridan Saint-Michel
Website Administrator
FoxJet, an ITW Company
www.foxjet.com
----- Original Message -----
From: "Christian Dechery" <[EMAIL PROTECTED]>
To: "Richard Lynch" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Friday, September 14, 2001 9:12 AM
Subject: [PHP] Re: is PHP crazy, or am I?
> I must have deleted the line by accident...
>
> $trocou=true; is right below $vetor[$j+1]=$aux;
>
> would that make sense?
>
> I'm not worried about the optimization here... I want to get time results
> for bubblesort... and then I'm going to heap, quick, and others... It's
> some college homework for my girlfriend...
>
>
> At 00:07 14/09/01 -0500, you wrote:
> >function bubblesort(&$vetor,$tam)
> >{
> > $trocou=true;
> > $i=$j=0;
> >
> > while($trocou)
> > {
> > $trocou=false;
> >
> ># You set $trocou to false here, and never reset it to true
> ># This loop will execute exactly once.
> >
> > for($j=0; $j<$tam-$i; $j++)
> > {
> > if($vetor[$j] > $vetor[$j+1])
> > {
> > $aux=$vetor[$j];
> > $vetor[$j]=$vetor[$j+1];
> > $vetor[$j+1]=$aux;
> > }
> > $i++;
> > }
> > }
> >}
> >
> > > it's right right?
> >
> >No.
> >
> >As near as I can figure, you are incrementing $j and decrementing $i on
> >every iteration.
> >That would mean that even if you fixed $trocou your sort algorithm would
be
> >O(n)
> >(Actually it's exactly 1/2 n, but that's the same as O(n) for
sufficiently
> >large n.)
> >
> >Alas, that can't be correct (we wish) and is not the standard bubble
sort...
> >
> >Try this for the body:
> >for ($i = 0; $i < $tam -1; $i++){
> > for ($j = $i + 1; $j < $tam -1; $j++){
> > if ($vetor[$i] < $vetor[$j]){
> > $aux = $vetor[$i];
> > $vetor[$i] = $vetor[$j];
> > $vetor[$j] = $aux;
> > }
> > }
> >}
> >
> >Forget the trocou bit.
> >
> > > so why when I print the array (with a for(;;) or with print_r) it
still
> > > shows me it's not ordered... I printed it INSIDE the function...
what's
> >the
> > > thing here? I'm I nuts?
> >
> >--
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> >[EMAIL PROTECTED]
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>
>
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