Consecutive Number Manipulation

skirkpatrick

I am trying to combine 2 number ranges and interleave them together to create a continuous list.

Here is my current code:

<?php
$quantity="10";
$startingnumber="1";
$endingnumber=$startingnumber + $quantity-1;
$endingnumberhalf=$startingnumber + $quantity-1;

$numbers = range($endingnumber, $startingnumber);
foreach ($numbers as $number) {
echo $number."<br>";
}
echo "<br>";
$numbershalf = range($endingnumberhalf/2, $startingnumber/2);
foreach ($numbershalf as $number) {
echo $number."<br>";
}
?>

Which produces this:
10
9
8
7
6
5
4
3
2
1

5
4
3
2
1

What I need it to do is this:

10
5
9
4
8
3
7
2
6
1

5
4
3
2
1

Any help whould be appreciated

laserlight

I am trying to combine 2 number ranges and interleave them together to create a continuous list.

You need to be more precise. How is this interleaving done? From your example it seems that all you want to do is alternate between the two lists where possible, and then dump the remaining elements from the larger list to the end of the combined list.

skirkpatrick

Laserlight,

You are 100% correct - I need to alternate between the lists and then dump at the end.

Thanks in advance

laserlight

If you do not have to actually interleave the two arrays, you could do something as simple as:

$quantity = 10;
$start = 1;

$i = $start + $quantity - 1;
$j = (int)($i / 2);

while ($j > 0)
{
    echo $i-- . "<br />\n" . $j-- . "<br />\n";
}

echo "<br />\n";

while ($i > 0)
{
    echo $i-- . "<br />\n";
}

skirkpatrick

That works perfectly

Thanks

NogDog

This seems to work:

<?php
function alternateArrays($arr1, $arr2)
{
   $result = array();
   $ix = 0;
   foreach($arr1 as $val)
   {
      $result[$ix] = $val;
      $ix += 2;
   }
   $ix = 1;
   foreach($arr2 as $val)
   {
      $result[$ix] = $val;
      $ix += 2;
   }
   ksort($result, SORT_NUMERIC);
   return(array_values($result));
}
// TEST:
$test1 = array(20,19,18,17,16,15,14,13);
$test2 = array(10,9,8,7,6);
$merged = alternateArrays($test1, $test2);
echo "<pre>";
print_r($merged);
echo "</pre>";
/* OUTPUT:
Array
(
    [0] => 20
    [1] => 10
    [2] => 19
    [3] => 9
    [4] => 18
    [5] => 8
    [6] => 17
    [7] => 7
    [8] => 16
    [9] => 6
    [10] => 15
    [11] => 14
    [12] => 13
)
*/