How to avoid generating adjacent duplicate elements when PHP arrays are shuffled?

PHP shuffle() may generate adjacent duplicate elements. To avoid this, you can use the following two methods: Use the a-Hash algorithm: generate a hash for each value and only keep the value corresponding to the unique hash value. Use mark and shuffle: Mark the used index and delete the marked index value before shuffling.

PHP avoids adjacent duplicate elements when the array is shuffled

In PHP, use shuffle() It is a common requirement for functions to shuffle array order. However, this function may generate adjacent duplicate elements. To avoid this we can use the following:

Implementation:

1. Use a-Hash:

function shuffle_array_avoid_adjacent_duplicates(array &$array) {
    $aHash = [];
    $result = [];
    foreach ($array as $key => $value) {
        $ah = md5($value);
        if (!isset($aHash[$ah])) {
            $aHash[$ah] = true;
            $result[] = $value;
        }
    }
    shuffle($result);
    return $result;
}

2. Using marking and shuffling:

function shuffle_array_avoid_adjacent_duplicates(array &$array) {
    $marked = [];
    foreach ($array as $key => $value) {
        $marked[$key] = false;
    }
    while (count($marked)) {
        $key = array_rand($marked);
        $result[] = $array[$key];
        unset($marked[$key]);
        unset($array[$key]);
    }
    shuffle($result);
    return $result;
}

Practical example:

$array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

$shuffled_array = shuffle_array_avoid_adjacent_duplicates($array);

print_r($shuffled_array);

Output:

Array
(
    [0] => 5
    [1] => 2
    [2] => 9
    [3] => 10
    [4] => 7
    [5] => 4
    [6] => 3
    [7] => 8
    [8] => 6
    [9] => 1
)

The above code uses the a-Hash algorithm to avoid adjacent duplicate elements and generate a disordered array.

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