在PHP阵列排列 [英] Array permutation in PHP

问题描述

考虑以下数组：

$a = [['x'], ['y', 'z', 'w'], ['m', 'n']];

如何生成以下从中数组：

How can generate following array from it:

$output=[
[[x][y][m]],
[[x][z][n]],
[[x][w][m]],
[[x][y][n]],
[[x][z][m]],
[[x][w][n]],
];

我正在寻找一种更有效的code比我的。 （我现在的code是psented如下答案$ P $）

I am searching for a more efficient code than mine. (My current code is presented as an answer below)

推荐答案

在这里，我们走了。假设：

Here we go. Assuming:

$array = [['x'], ['y', 'z', 'w'], ['m', 'n']];

编辑：经过一些性能测试，我总结我以前张贴的解决方案比OP的code慢约300％，无疑因嵌套函数调用堆栈。因此，这里是OP的做​​法，这是周围的改进版本的 40％的速度

After some performance testing, I concluded the solution I posted before is about 300% slower than OP's code, surely due to nested function call stacking. So here is an improved version of OP's approach, which is around 40% faster:

$count     = array_map('count', $array);
$finalSize = array_product($count);
$arraySize = count($array);
$output    = array_fill(0, $finalSize, []);
$i = 0;
$c = 0;
for (; $i < $finalSize; $i++) {
    for ($c = 0; $c < $arraySize; $c++) {
        $output[$i][] = $array[$c][$i % $count[$c]];
    }
}

这是基本相同的code，但我用本地函数可能时，也拿出了一些循环功能，已经不能在每次迭代执行。

It is basically the same code but I used native functions when possible and also took out the loops some functionality that hadn't to be executed on each iteration.

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