How to order a string of numbers by the sum of their digits

Question

I need to output the numbers by order of their sums.

    <?php
    $str = '11 11 2004 6 99 43 88 10003';
    function orderWeight($str) {
        $nums = explode(" ", $str);
        $newArray= [];
        foreach($nums as $key => $value){
            $key = array_sum(str_split($value));
            if(array_key_exists($key,$newArray)){
                $key = $key + 0.5;

                $newArray += array($key => $value);
            }else{

                $newArray += array($key => $value);
            }

        }
        ksort($newArray);
        $ans = implode(' ',$newArray);
        print_r($ans);
    }
    echo(orderWeight($str));

The result is

11 10003 2004 43 88 99

It is sorted correctly but some numbers are overwritten by the keys that match by the sum.

you are sorting lexical values, i.e. strings, thus 10003 comes before 2004 etc ... — px1mp, Jun 03 '20 at 16:19
You don't need to reinvent the wheel here. See the description of `usort` on the linked question. — IMSoP, Jun 03 '20 at 17:15
I cannot post an answer to this question. https://3v4l.org/OfEXL — mickmackusa, Jul 11 '22 at 21:50

Andrey Yerokhin · Answer 1 · 2020-06-03T16:53:13.250

Floats in keys of array in PHP are truncated to integer. So you get duplicate keys for 2 and 2.5 (both truncate to 2). You need to use string keys instead and then use custom function to compare.

Also you need to change if with while (you can have more than 2 duplicate values within input string).

Here is code that should works:

<?php
$str = '11 11 2004 6 99 43 88 10003';
function orderWeight($str) {
    $nums = explode(" ", $str);
    $newArray = [];
    foreach ($nums as $key => $value) {
        $key = array_sum(str_split($value));
        while (array_key_exists((string)$key, $newArray)) {
            $key = $key + 0.001;
        }
        $newArray += [(string)$key => $value];
    }
    uksort($newArray, function ($a, $b) {return $a - $b;});
    $ans = implode(' ', $newArray);
    return $ans;
}
echo orderWeight($str);

How to order a string of numbers by the sum of their digits

1 Answers1