How many times can x unique values be pulled from an array

Question

I have an array of values (non unique) and I need to work out how many times I can pull out x (eg 3) unique items from that array.

eg

[5, 5, 4, 1, 2, 3, 4, 2, 1, 3, 5, 5]

What is the largest quantity of unique items of length 3 (eg [5, 4, 1] ) I can retrieve?

For context, this is for an offer system in a shopping cart. The array of values is the product ids, and I need to know how many times I can apply a specific offer that requires 3 different items from the array of ids in order to be valid.

Thanks for any help - just ask if anything is unclear and I'll try to explain. If I've missed an existing question that answers this please let me know and I'll close this question.

Answer 1

Here's one way you can follow:

$basket = array(5, 5, 4, 1, 2, 3, 4, 2, 1, 3, 5, 5);
$length = 3; //unique set size

function getSetCount($basket, $length) {
    $counts = array_count_values($basket); //count of each ID
    $totalCount = count($basket); //count of all elements

    //maximum amount of sets
    $max = floor($totalCount / $length);

    //since every ID can be only once in a set, it all above $max occurences won't be able to fit any set.
    $reducedCounts = array_map(function ($el) use ($max) {
        return min($el, $max);
    }, $counts);

    //final result is "all elements that should fit in sets / size of set
    return floor(array_sum($reducedCounts) / $length);
}

If you would like to print them:

function printSets($basket, $length) {
    $counts = array_count_values($basket); //count of each ID

    while(!empty($counts)) {
        arsort($counts);//reverse sort with keeping the keys
        $set = array_slice(array_keys($counts),0,$length); //get the set
        echo implode(',', $set) . '<br/>';
        foreach($set as $id) { //reduce counts
            $counts[$id]--;
        }
        $counts = array_filter($counts); //clean zeros
    }
}

The code above may not handle proparly some edge cases. But this is the idea.

Basically array_count_values() counts values' occurences and returns an array of value => count pairs. Then its easy to manipulate this data.

Answer 2

If i understand you correctly:

function getChunksCount($products)
{   
    // get unique ids
    $uniqueProducts = array_unique($products);

    // count unique ids
    $count = count($uniqueProducts);

    // let's get the number of chucks available
    $chunkSize = 3;

    // round to the floor
    return floor($count / $chunkSize);
}

No complex logic or processing at all. Next time try to write down what exactly needs to be done in what order, and the solution might become pretty obvious :)

Answer 3

You can do it using array_unique and array_slice .

$arr = [5, 5, 4, 1, 2, 3, 4, 2, 1, 3, 5, 5];

$new_arr = array_slice(array_unique($arr), 0, 3);
print_r($new_arr); //Array ( [0] => 5 [1] => 4 [2] => 1 )

Answer 4

You can use array_count_values .

<?php `$array = array(5, 5, 4, 1, 2, 3, 4, 2, 1, 3, 5, 5); $vals = array_count_values($array); echo 'No. of NON Duplicate Items: '.count($vals).'<br><br>'; print_r($vals);`?>

Output is -Array ( [5] => 4 [4] => 2 1 => 2 [2] => 2 [3] => 2 )