php数组递归

<?php
function printArray($arr) {
    foreach ($arr as $value) {
        if (is_array($value)) {
            printArray($value); // 递归调用
        } else {
            echo $value . "\n";
        }
    }
}

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

printArray($array);
?>

<?php
function printArrayIterative($arr) {
    $stack = array_merge([$arr], array_map('array_reverse', array_values($arr)));
    while (!empty($stack)) {
        $current = array_pop($stack);
        if (is_array($current)) {
            $stack = array_merge($stack, array_map('array_reverse', array_values($current)));
        } else {
            echo $current . "\n";
        }
    }
}

printArrayIterative($array);
?>

<?php
function factorial($n, $acc = 1) {
    if ($n <= 1) {
        return $acc;
    }
    return factorial($n - 1, $n * $acc); // 尾递归
}

echo factorial(5); // 输出 120
?>