note 18083 added to ref.strings
| From: | carl at youngbloods dot org | Date: | Thu, 10 Jan 2002 01:27:28 +0000 |
| Subject: | note 18083 added to ref.strings | ||
| Groups: | php.notes | ||
| Request: | Send a blank email to php-notes+get-24605@lists.php.net to get a copy of this message | ||
I've ported a function to PHP that will find the longest common substring in two different
strings. Here it is:
function LongestCommonSubstring($string1, $string2)
{
// find length of longest common substring first
$L = array();
$length1 = strlen($string1);
$length2 = strlen($string2);
for ($i = $length1; $i >= 0; $i--)
{
for ($j = $length2; $j >= 0; $j--)
{
if ($string1[$i] == '' || $string2[$j] == '') $L[$i][$j] = 0;
elseif ($string1[$i] == $string2[$j]) $L[$i][$j] =
1 + $L[$i + 1][$j + 1];
else $L[$i][$j] = max($L[$i + 1][$j], $L[$i][$j + 1]);
}
}
// then find the actual substring
$substring = '';
$i = 0;
$j = 0;
while ($i < $length1 && $j < $length2)
{
if ($string1[$i] == $string2[$j])
{
$substring .= $string1[$i];
$i++; $j++;
}
elseif ($L[$i + 1][$j] >= $L[$i][$j + 1]) $i++;
else $j++;
}
return $substring;
}
Here is where I found the original:
http://www1.ics.uci.edu/~eppstein/161/960229.html
--
http://www.php.net/manual/en/ref.strings.php
http://master.php.net/manage/user-notes.php?action=edit+18083
http://master.php.net/manage/user-notes.php?action=delete+18083
http://master.php.net/manage/user-notes.php?action=reject+18083