How Can I Efficiently Merge Two Flat Indexed Arrays Alternately?

Merging Flat Indexed Arrays Alternately

Merging two arrays in an alternating fashion, pushing values into the result one by one rather than concatenating them, is a common requirement in data processing and manipulation. In this case, we have two flat indexed arrays, $a1 and $a2, and we want to merge them into a new array, $newArray, such that the values are interleaved as follows: [0, 3, 1, 4, 2, 5].

While it's possible to achieve this using a manual loop as suggested, there's a more efficient native approach that offers performance advantages. The following code showcases the precomputed approach:

$count = count($a1);
for ($i = 0; $i < $count; $i++) {
    $newArray[] = $a1[$i];
    $newArray[] = $a2[$i];
}

In this code, we first determine the count of elements in $a1 (assuming $a1 and $a2 have the same size). Then, we use a loop to iterate over the elements and add them alternately to the $newArray.

Performance benchmarking, as shown below, confirms the efficiency of this approach:

$a1 = array(0, 1, 2);
$a2 = array(3, 4, 5);

$start = microtime(TRUE);

for($t = 0; $t < 100000; $t++){
    $newArray = array();
    $count = count($a1);
    for ($i = 0; $i < $count; $i++){
        $newArray[] = $a1[$i];
        $newArray[] = $a2[$i];
    }
}
echo round(microtime(TRUE) - $start, 2); # 0.6

Compared to the approach that recounts array size in each iteration, this precomputed approach offers a substantial performance improvement:

$a1 = array(0, 1, 2);
$a2 = array(3, 4, 5);

$start = microtime(TRUE);

for($t = 0; $t < 100000; $t++){
    $newArray = array();
    for ($i = 0; $i < count($a1); $i++){
        $newArray[] = $a1[$i];
        $newArray[] = $a2[$i];
    }
}
echo round(microtime(TRUE) - $start, 2); # 0.85

While benchmarking provides a snapshot of performance, it's important to note that the specific performance characteristics may vary depending on the specific data and environment. Nonetheless, this precomputed approach offers a solid foundation for efficiently merging flat indexed arrays in an alternating fashion.

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