Help with an array algorithm

[victorianrider]

Alright, so I have 100 user ids which I need sorted in a very specific way. Right now, they're organized in a 1-100 format. Let's think of each ID as ID#1, ID#2, ID#3 etc all the way up to ID#100. I need to code a script to echo them out in the following order:

$ID2.'<br/>';

$ID1.'<br/>';

$ID4.'<br/>';

$ID3.'<br/>';

$ID6.'<br/>';

$ID5.'<br/>';

//etc up to

$ID100.'<br/>';

$ID99.'<br/>';

 

Is there any special algorithm or trick with an array to do this? I will attach a file with each ID seperated by a semi-colon. And also here is the script I have right now which echo's them out in order:

<?PHP
$File = "IDs.txt";
$Login = file($File);
$String = file_get_contents($File);
$Logins = explode(";", $String);
foreach($Logins as $Login)
{
echo $Login.'<br/>';
}
?>

 

[attachment deleted by admin]

[BlueSkyIS]

if i understand, you want each pair to be in reverse order: 21436587

 

if so, i would use a for loop, incrementing by i + 2, then take array[i + 1] followed by array on each loop.

[ronverdonk]

Something line:

$a=array('id1','id2','id3','id4','id5','id6','id7','id8','id9','id10','id11','id12');
for ($i=0, $j=1; $i<count($a); $i+=2,$j+=2) {
    echo "<br>$a[$j]";
    echo "<br>$a[$i]";
}

[victorianrider]

if i understand, you want each pair to be in reverse order: 21436587

 

if so, i would use a for loop, incrementing by i + 2, then take array[i + 1] followed by array on each loop.

That sounds about right, however I'm having a bit of trouble interpreting your suggestion into an actual script, could you please provide an example? That would be great.

Cheers

[BlueSkyIS]

Something line:

$a=array('id1','id2','id3','id4','id5','id6','id7','id8','id9','id10','id11','id12');
for ($i=0, $j=1; $i<count($a); $i+=2,$j+=2) {
    echo "<br>$a[$j]";
    echo "<br>$a[$i]";
}

 

i was thinking more like:

 

$a=array('id1','id2','id3','id4','id5','id6','id7','id8','id9','id10','id11','id12');
$a_cnt = count($a);
$sorted_vals = array()
for ($i=0;$i<$a_cnt;$i++) {
      $sorted_vals[] = $a[$i + 1];
      $sorted_vals[] = $a[$i];
}

 

...but if you have an odd number of values in the array, you'll need to account for that.

[victorianrider]

Something line:

$a=array('id1','id2','id3','id4','id5','id6','id7','id8','id9','id10','id11','id12');
for ($i=0, $j=1; $i<count($a); $i+=2,$j+=2) {
    echo "<br>$a[$j]";
    echo "<br>$a[$i]";
}

Something line:

$a=array('id1','id2','id3','id4','id5','id6','id7','id8','id9','id10','id11','id12');
for ($i=0, $j=1; $i<count($a); $i+=2,$j+=2) {
    echo "<br>$a[$j]";
    echo "<br>$a[$i]";
}

 

i was thinking more like:

 

$a=array('id1','id2','id3','id4','id5','id6','id7','id8','id9','id10','id11','id12');
$a_cnt = count($a);
$sorted_vals = array()
for ($i=0;$i<$a_cnt;$i++) {
      $sorted_vals[] = $a[$i + 1];
      $sorted_vals[] = $a[$i];
}

 

...but if you have an odd number of values in the array, you'll need to account for that.

Yes thank you both, I will save both versions, as of right now it is working. Much appreciated for your time and help