John Davidson

Message:

I have a fixed number (5) and a fixed length (2):

I want to find all the combinations that can sum 50 (this can vary of course).

For example, for 50, and a length of 2, I want to get:

[[1, 49], [2, 48], [3, 47], [4, 46], ...],

For 50 and a length of 4, I want to get:

[[1, 1, 1, 47], [1, 1, 2, 46], [1, 1, 3, 45], [1, 1, 4, 44], ...],

I have no clue how to do this, or whether there's a name in mathematics for this.

This is what I have (doesn't have to use generators):

function getCombinations(array $numbers, int $sum, int $setLength) : \Generator {

    $numbersLowestFirst = $numbers;

    asort($numbersLowestFirst);

    $lowestNumber = 0;

    foreach ($numbersLowestFirst as $number) {

        // array might be associative and we want to preserve the keys

        $lowestNumber = $number;

        break;

    }



    $remainingAmount = $sum - $lowestNumber;

    $remainingNumberofItems = $setLength - 1;



    $possibleItemCombinations = array_pad([$remainingAmount], $remainingNumberofItems, $lowestNumber);



}

---

My Answer:
Here is an updated version of your function that generates all possible combinations of numbers that sum up to a given total, with a fixed length:

php
function getCombinations(int $total, int $length) : \Generator {
$numbers = range(1, $total - 1);

foreach ($numbers as $number) {
if ($length == 1) {
yield [$number];
} else {
foreach (getCombinations($total - $number, $length - 1) as $combination) {
array_unshift($combination, $number);
yield $combination;
}
}
}
}

$total = 50;
$length = 2;

foreach (getCombinations($total, $length) as $combination) {
print_r($combination);
}


This function uses recursion to generate all possible combinations of numbers that sum up to the given total, with the specified length. You can adjust the `$total` and `$length` variables to get combinations for different totals and lengths.