Sorting an array of numbers with for-loop

Question

I have a task of sorting an array of numbers in both ascending and descending order. The challenge is, I can't use the built-in sort function, but loop through the array with for-loops instead.

I am a total newbie when it comes to PHP and this task straight off baffles me. Here is the code I'm supposed to work with:

<?php
  $arr = $_GET['arr'];
  $table = explode(',', $arr);
  
  $count = count($table);
  
  // What I tried to work with, didn't get to work:
  for ($i = 0; $i < $count; $i++) {
      for ($j = $i + 1; $j < $count; $j++) {
          if ($table[$i] > $table[$j]) {
              $temp = $table[$i];
              $table[$i] = $table[$j];
              $table[$j] = $temp;
              $asc = implode("," $temp);
          }
      }
  }
  
  echo "Ascending: $asc";
  echo "Descending: $desc";
?>

Any clue why this doesn't run? At some point, I got the first (largest) number in the array with the echo, but don't really know what broke that either.

Carsten Massmann · Accepted Answer · 2021-10-14 11:08:20Z

1

Move the line

$asc = implode(",", $table);

from its current location below the outer for loop and maybe add the line

$desc = implode(",", array_reverse($table));

to get the descending sort order.

edited Oct 14, 2021 at 11:08

answered Oct 13, 2021 at 19:29

Carsten Massmann

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1 Comment

Pepelius Over a year ago

This seemed to be the issue - big thanks for mentioning the array_reverse method as well, didn't even cross my mind! I would've just done the same for loop twice with different operator to accomplish this.

Maik Lowrey · Accepted Answer · 2021-10-13 19:49:28Z

Many ways to make it. One solution you will find in the code below. you will certainly notice that the sorting depends only on one operator. Therefore, you can build a function out of it by specifying the sorting as a parameter. function(array $array, string $sort) {}

DESC

    $arr= array(112,21,130,140,2,42);
    for($i=0; $i<count($arr)-1; $i++)
    {
        for($j=0; $j<count($arr)-1; $j++)
        {
            if($arr[$j] < $arr[$j+1]){
                $temp= $arr[$j+1];
                $arr[$j+1]= $arr[$j];
                $arr[$j]= $temp;
            }
        }

    }
    print_r($arr);

Output:

Array
(
    [0] => 140
    [1] => 130
    [2] => 112
    [3] => 42
    [4] => 21
    [5] => 2
)

ASC

    $arr= array(112,21,130,140,2,42);
    for($i=0; $i<count($arr)-1; $i++)
    {
        for($j=0; $j<count($arr)-1; $j++)
        {
            if($arr[$j] > $arr[$j+1]){
                $temp= $arr[$j+1];
                $arr[$j+1]= $arr[$j];
                $arr[$j]= $temp;
            }
        }

    }
    print_r($arr);

Output

Array
(
    [0] => 2
    [1] => 21
    [2] => 42
    [3] => 112
    [4] => 130
    [5] => 140
)

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