PHP:使用 levenshtein 距离来匹配单词

Question

我一直在阅读和测试 php levenshtein 中的一些示例。比较 $input 和 $words输出比较

$input = 'hw r u my dear angel';

    // array of words to check against
    $words  = array('apple','pineapple','banana','orange','how are you',
                    'radish','carrot','pea','bean','potato','hw are you');

输出

Input word: hw r u my dear angel
Did you mean: hw are you?

比较，删除数组中的hw are you。

$input = 'hw r u my dear angel';

    // array of words to check against
    $words  = array('apple','pineapple','banana','orange','how are you',
                    'radish','carrot','pea','bean','potato');

在第二次删除数组输出中的 hw are you

Input word: hw r u my dear angel
Did you mean: orange? 

在 similar_text() 中的位置

 echo '<br/>how are you:'.similar_text($input,'how are you');
    echo '<br/>orange:'.similar_text($input,'orange');
    echo '<br/>hw are you:'.similar_text($input,'hw are you');

how are you:6
orange:5
hw are you:6

在第二次比较时，为什么它输出 orange 而 how are you 也有 6 个类似的文本，如 hw are you？有什么方法可以改进或更好的方法吗？我也将所有可能的输入保存在数据库中。我应该查询它并存储在 array 中，然后使用 foreach 来获取 levenshtein distance？但如果有数百万，那会很慢。

代码

  <?php
    // input misspelled word
    $input = 'hw r u my dear angel';

    // array of words to check against
    $words  = array('apple','pineapple','banana','orange','how are you',
                    'radish','carrot','pea','bean','potato','hw are you');


    // no shortest distance found, yet
    $shortest = -1;

    $closest = closest($input,$words,$shortest);


    echo "Input word: $input<br/>";
    if ($shortest == 0) {
        echo "Exact match found: $closest\n";
    } else {
        echo "Did you mean: $closest?\n";
    }
    echo '<br/><br/>';

    $shortest = -1;
    $words  = array('apple','pineapple','banana','orange','how are you',
                    'radish','carrot','pea','bean','potato');
    $closest = closest($input,$words,$shortest);
    echo "Input word: $input<br/>";
    if ($shortest == 0) {
        echo "Exact match found: $closest\n";
    } else {
        echo "Did you mean: $closest?\n";
    }

    echo '<br/><br/>';
    echo 'Similar text';
    echo '<br/>how are you:'.similar_text($input,'how are you');
    echo '<br/>orange:'.similar_text($input,'orange');
    echo '<br/>hw are you:'.similar_text($input,'hw are you');



    function closest($input,$words,&$shortest){
        // loop through words to find the closest
    foreach ($words as $word) {

        // calculate the distance between the input word,
        // and the current word
        $lev = levenshtein($input, $word);

        // check for an exact match
        if ($lev == 0) {

            // closest word is this one (exact match)
            $closest = $word;
            $shortest = 0;

            // break out of the loop; we've found an exact match
            break;
        }

        // if this distance is less than the next found shortest
        // distance, OR if a next shortest word has not yet been found
        if ($lev <= $shortest || $shortest < 0) {
            // set the closest match, and shortest distance
            $closest  = $word;
            $shortest = $lev;
        }


    }
    return $closest;
    }
    ?>

Answer 1

首先，similar_text() 输出什么并不重要，因为它使用另一种算法来计算字符串之间的相似度。

让我们试着理解为什么 levenstein() 认为 hw r u my Dear ange 更接近 orange 而不是 '你好吗。维基百科有一个 good definition莱文斯坦距离是多少。

Informally, the Levenshtein distance between two words is the minimum number of single-character edits (insertion, deletion, substitution) required to change one word into the other.

现在让我们计算一下我们需要进行多少次编辑才能将 hw r u my Dear angel 变为 orange。

1. hw r u my Dear angel → hw r u my Dear angel(删除最后一个字符)
2. hw r u my Dear ange → hw r u my dearange(删除最后一个空格)
3. hw r u my dearange → arange(删除前 12 个字符)
4. arange → 橙色(用 o 代替 a)

所以总共需要 1 + 1 + 12 + 1 = 15 次编辑才能将 hw r u my Dear angel 变为 orange。 p>

这是你亲爱的天使到你好吗的转变。

1. hw r u my Dear angel → how r u my Dear 天使(插入 o 字符)
2. 亲爱的天使你好吗→亲爱的天使(删除7个字符)
3. how Dear angel → how ar angel(删除2个字符)
4. how ar angel → how are angel(插入 e 字符)
5. how are angel → how are ang(删除最后 2 个字符)
6. how are ang → how are you(替换最后 3 个字符)

总 1 + 7 + 2 + 1 + 5 = 16 次编辑。因此，正如您所看到的莱文斯坦距离 orange 更接近 hw r u my Dear angel ;-)