How can I generate all possible combinations and permutations of elements within a one-dimensional array in PHP?

PHP: How to Obtain All Possible Combinations of a One-Dimensional Array

In this article, we will dive into a method to retrieve all possible combinations of elements within a one-dimensional array in PHP. In contrast to other solutions, this approach ensures that both combinations and permutations are considered.

Problem Statement

Given an array of strings or numbers, the goal is to generate all possible combinations of elements, taking into account different arrangements. For instance, 'Alpha Beta' and 'Beta Alpha' are distinct combinations that should be included in the output.

PHP Solution

The provided PHP solution employs a recursive depth-first search algorithm:

<code class="php"><?php $array = array('Alpha', 'Beta', 'Gamma', 'Sigma');

function depth_picker($arr, $temp_string, &$collect) {
    if ($temp_string != "") 
        $collect []= $temp_string;

    for ($i=0, $iMax = sizeof($arr); $i < $iMax; $i++) {
        $arrcopy = $arr;
        $elem = array_splice($arrcopy, $i, 1); // removes and returns the i'th element
        if (sizeof($arrcopy) > 0) {
            depth_picker($arrcopy, $temp_string ." " . $elem[0], $collect);
        } else {
            $collect []= $temp_string. " " . $elem[0];
        }   
    }   
}

$collect = array();
depth_picker($array, "", $collect);
print_r($collect);

?></code>

Breakdown of the Solution

• The depth_picker function is invoked with the initial array, an empty string, and an empty array reference.
• It recursively loops through the array, adding each element to the end of the current result string.
• Whenever the temp string has elements, it is added to the result array.
• If there are still elements left in the input array, the function calls itself with the updated array and temp string.
• If there are no more elements left, the temp string containing the complete combination is added to the collect array.

Output

The code provided produces the following output, which contains all combinations and permutations of the elements in the given array:

Array
(
    [0] =>  Alpha
    [1] =>  Alpha Beta
    [2] =>  Alpha Beta Gamma
    [3] =>  Alpha Beta Gamma Sigma
    [4] =>  Alpha Beta Sigma
    [5] =>  Alpha Beta Sigma Gamma
    [6] =>  Alpha Gamma
    [7] =>  Alpha Gamma Beta
    [8] =>  Alpha Gamma Beta Sigma
    [9] =>  Alpha Gamma Sigma
    [10] =>  Alpha Gamma Sigma Beta
    [11] =>  Alpha Sigma
    [12] =>  Alpha Sigma Beta
    [13] =>  Alpha Sigma Beta Gamma
    [14] =>  Alpha Sigma Gamma
    [15] =>  Alpha Sigma Gamma Beta
    [16] =>  Beta
    [17] =>  Beta Alpha
    [18] =>  Beta Alpha Gamma
    [19] =>  Beta Alpha Gamma Sigma
    [20] =>  Beta Alpha Sigma
    [21] =>  Beta Alpha Sigma Gamma
    [22] =>  Beta Gamma
    [23] =>  Beta Gamma Alpha
    [24] =>  Beta Gamma Alpha Sigma
    [25] =>  Beta Gamma Sigma
    [26] =>  Beta Gamma Sigma Alpha
    [27] =>  Beta Sigma
    [28] =>  Beta Sigma Alpha
    [29] =>  Beta Sigma Alpha Gamma
    [30] =>  Beta Sigma Gamma
    [31] =>  Beta Sigma Gamma Alpha
    [32] =>  Gamma
    [33] =>  Gamma Alpha
    [34] =>  Gamma Alpha Beta
    [35] =>  Gamma Alpha Beta Sigma
    [36] =>  Gamma Alpha Sigma
    [37] =>  Gamma Alpha Sigma Beta
    [38] =>  Gamma Beta
    [39] =>  Gamma Beta Alpha
    [40] =>  Gamma Beta Alpha Sigma
    [41] =>  Gamma Beta Sigma
    [42] =>  Gamma Beta Sigma Alpha
    [43] =>  Gamma Sigma
    [44] =>  Gamma Sigma Alpha
    [45] =>  Gamma Sigma Alpha Beta
    [46] =>  Gamma Sigma Beta
    [47] =>  Gamma Sigma Beta Alpha
    [48] =>  Sigma
    [49] =>  Sigma Alpha
    [50] =>  Sigma Alpha Beta
    [51] =>  Sigma Alpha Beta Gamma
    [52] =>  Sigma Alpha Gamma
    [53] =>  Sigma Alpha Gamma Beta
    [54] =>  Sigma Beta
    [55] =>  Sigma Beta Alpha
    [56] =>  Sigma Beta Alpha Gamma
    [57] =>  Sigma Beta Gamma
    [58] =>  Sigma Beta Gamma Alpha
    [59] =>  Sigma Gamma
    [60] =>  Sigma Gamma Alpha
    [61] =>  Sigma Gamma Alpha Beta
    [62] =>  Sigma Gamma Beta
    [63] =>  Sigma Gamma Beta Alpha
)

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