Question

我想在php中动态使用 foreach 循环，我有权将AAA打印到 999 ，并且我正在使用此代码及其工作完美，

Reference :: http://www.onlinecode.org/generate-string-aaaa-9999-using-php-code/

$addalphabeth = array_merge(range('A', 'Z'), range(0,9));
$setcharacter = [];
foreach ($addalphabeth as $setcharacter[0]) {
  foreach ($addalphabeth as $setcharacter[1]) {
    foreach ($addalphabeth as $setcharacter[2]) {
        //$setcatalog[] = vsprintf('%s%s%s', $setcharacter);
        echo "<b>".vsprintf('%s%s%s', $setcharacter)."</b>";
        echo "<br>";
    }
  }
}

现在我的问题是必须将 AAAAA 打印到 99999 （需要循环5次）或 AAAAAAAA 打印到 99999999 （需要循环8次），所以对于这个我使用循环 n时间。我不知道该怎么做，任何帮助或建议将不胜感激。

Answer 1

Evening, here is my solution, using recursion. To setup a recursion, you have to think of two things. What is your stop condition, and what do to with non-stopping conditions.

Stopping condition: when you ask for only 1 char width, simply loop through each member of $addalphabeth. And since that width == 1 scenario will happen when the final width you want is >1, add the prefix to it.
Non-stopping condition: lets start with width 2. You want the every first char to be followed by all possible second chars. So call the function with width = 1 and prefix = the first char.
for 3, you want the first char followed by every char in the second position, followed by every char in the third position.
and so on...
So the general case is: from left to right, with n chars width, loop on every char, and print every possible combination of n-1 chars after it.

So here is the code:

function printAto9($width,$prefix = '')
{
    $chars = array_merge(range('A', 'Z'), range(0,9));
    if ($width == 1)
    {
        foreach ($chars as $char)
        {
            echo "$prefix$char\n";
        }
    }
    else
    {
        $width--;
        foreach ($chars as $char)
        {
            echo printAto9($width,$prefix . $char);
        }
    }
}

printAto9(5);

I put printAto9(5); as a test, you can use whatever. But careful, the output is monstrous pretty quick, and you can kill your php (memory or time limit).

在php中动态使用foreach循环

1 个答案: