entiendoNull entiendoNull - 1 year ago 62
PHP Question

Finding out combinations of x amount of integers to sum a given number

I am trying to figure out how I can loop out possible combinations of a x amount of integers to sum a specifik number.

Let's say, I have number 7 and I need to figure out how I can sum that number with integers in pairs 3.
1+2+4 = 7

3+3+1 = 7

5+1+1 = 7

2+2+3 = 7

Repeated combinations of numbers doesn't interest me, e.g.:

1+2+4 = 7

2+4+1 = 7

4+2+1 = 7

Anyone got any ideas of how I should proceed to reach this result?
Thanks.

Answer Source

I've got a solution to my problem. I feel I should defientely share it here, if anyone would ever need it. My solutions is based on this post: https://stackoverflow.com/a/19067884/3293843

<?php
function sampling($chars, $size, $combinations = array()) {
    # if it's the first iteration, the first set 
    # of combinations is the same as the set of characters
    if (empty($combinations)) {
        $combinations = $chars;
    }

    # we're done if we're at size 1
    if ($size == 1) {
        return $combinations;
    }

    # initialise array to put new values in
    $new_combinations = array();

    # loop through existing combinations and character set to create strings
    foreach ($combinations as $combination) {
        foreach ($chars as $char) {
            $new_combinations[] = $combination .'@'. $char;
        }
    }

    # call same function again for the next iteration
    return sampling($chars, $size - 1, $new_combinations);

}

// example
$chars = array('1', '2', '3','4');
$target = 7;
$maxLengthOfIntegers = 3;
$output = sampling($chars, $maxLengthOfIntegers);
$repeatedEntries = array();


//presenting the output
foreach($output as $out){
    $explodeOut = explode('@',$out);
    sort($explodeOut);
    if(array_sum($explodeOut) == $target){
        $sortedPattern = implode('',$explodeOut);
        if(!in_array($sortedPattern,$repeatedEntries)){
            echo $sortedPattern.'<br/>';
            $repeatedEntries[] = $sortedPattern;
            }
        }
    }
?>

Thank you for your time and efforts.

Regards, Jacob

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