php - 将单词转换为字典顺序的数字

Question

我正在尝试计算一个单词的“分数”，以便它将用于确定它在 Redis 排序集中的字典顺序(按字母顺序列出的单词)。

阅读 this post它说:

How to turn a word into a score?

For instance, if you want to use the first four letters to produce the score, this is the rule:

score = first-byte-value*(256^3) + second-byte-value*(256^2) + third-byte-value*(256^1) + fourth-byte-value

Just omit from the sum non existing chars if the word is < 4 chars in length.

Why this works? You are just considering the bytes as digits of a radis-256 number :)

根据这个理论，我想出了以下代码来测试它是否适用于 PHP 数组:

$words = array('abcd', 'hello', 'dogs', 'hiya');
$newWords = array();

foreach ($words as $word) {
    $len = strlen($word);

    if ($len > 4) {
        $len = 4;
    }

    $i = 0;
    $j = $len - 1;
    $score = 0;

    while ($i < $len) {
        $byte = ord($word[$i]);

        if ($j == 0) {
            $score += $byte;
        }
        else {
            $score += $byte * (256 ^ $j);
        }

        $i++;
        $j--;
    }

    $newWords[$score] = $word;
}

ksort($newWords);
print_r($newWords);

但是这会返回:

Array
(
    [75950] => abcd
    [80858] => hello
    [81124] => dogs
    [85220] => hiya
)

这不是按字母顺序排列的。

谁能发现问题(显然分数计算有误)？我可能误解了帖子:-/

Answer 1

我稍微改进了代码并改为使用 pow

$words = array('abcd', 'hello', 'dogs', 'hiya');
$newWords = array(); 
foreach ($words as $word) {

$len = strlen($word);

    if ($len > 4) {
        $len = 4;
    }

    $i = 0;
    $j = $len - 1;
    $score = 0;

    while ($i < $len) {
        $byte = ord($word[$i]);
        $score += $byte * pow(256, $j);
        $i++;
        $j--;
    }

    $newWords[$score] = $word;
}
ksort($newWords);
print_r($newWords);

它完全符合您的预期:

Array ( [1633837924] => abcd [1685022579] => dogs [1751477356] => hello [1751742817] => hiya )

你实际上使用了 XOR http://www.php.net/manual/en/language.operators.bitwise.php