The PHP implementation of editing distance and Hamming distance

When calculating the similarity of a string or graph, the two commonly used algorithms, one is the editing distance, the other is the Hamming distance.

Simply put:

Editing distance is the ability to turn a string into another string with several edits

Hamming distance is the corresponding position to compare, find out the different number of characters

To find out more, please search by yourself.

The following are their PHP code implementations.

<?php/** *  Calculate editing distance  * *  @param  string  $s 1 *  @param  string   $s 2 */function levdist ($s 1,  $s 2) {     $len 1 = strlen ($s 1);      $len 2 = strlen ($s 2);     if ($len 1 == 0)      {        return  $len 2;    }     if ($len 2 == 0)     {         return  $len 1;    }    for ($i  = 0;  $i  <=  $len 1;  $i + +)     {        $ matrix[$i][0] = 0;    }    for ($j  = 0;  $j  <=  $len 2;  $j + +)     {        $ matrix[0][$j] = 0;     }    for ($i  = 1;  $i  <=  $len 1;  $i + +)     {         $ch 1 =  $s 1[$i  -  1];        for ($j  = 1;  $j  <=  $len 2;   $J + +)         {              $ch 2  =  $s 2[$j  - 1];              $temp  =  $ch 1 ==  $ch 2 ? 0 : 1;              $arr  = array (                  $matrix [$i  - 1][ $j] + 1,                  $matrix [$i] [$j  - 1] + 1,                  $matrix [$i  - 1][$j  - 1] +  $temp              );             $ matrix[$i] [$j] = min ($arr);        }     }    return  $matrix [$len 1][$len 2];} /** *  calculating Hamming distance  * *  @param  string  $s 1 *  @param  string  $s 2  *  @return  boolean number */function hamdist ($s 1,  $s 2) {      $len 1 = strlen ($s 1);     $len 2 = strlen ($s 2);     if ($len 1 !=  $len 2)     {         return false;    }     $dist &nbsP;= 0;    for ($i  = 0;  $i  <  $len 1;  $i + +)      {        if ($s 1[$i] !=  $s 2[$i])          {            $ dist++;        }    }     return  $dist;} $s 1 =  "abcde", $s 2 =  "acdeb", echo levdist ($s 1,  $s 2);//  output 2echo hamdist ( $s 1,  $s 2);//  output 4

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The PHP implementation of editing distance and Hamming distance