我在这里找到一个脚本,在寻找最低公共子串时效果很好.
但是,我需要它来容忍一些不正确/缺少的字符.我希望能够输入所需的相似性百分比,或者可以指定允许的丢失/错误字符的数量.
例如,我想找到这个字符串：
大黄校车
在这个字符串里面：
那天下午他们骑着bigyellow schook巴士
这是我目前正在使用的代码：
function longest_common_substring($words) {
$words = array_map('strtolower', array_map('trim', $words));
$sort_by_strlen = create_function('$a, $b', 'if (strlen($a) == strlen($b)) { return strcmp($a, $b); } return (strlen($a) < strlen($b)) ? -1 : 1;');
usort($words, $sort_by_strlen);
// We have to assume that each string has something in common with the first
// string (post sort), we just need to figure out what the longest common
// string is. If any string DOES NOT have something in common with the first
// string, return false.
$longest_common_substring = array();
$shortest_string = str_split(array_shift($words));
while (sizeof($shortest_string)) {
array_unshift($longest_common_substring, '');
foreach ($shortest_string as $ci => $char) {
foreach ($words as $wi => $word) {
if (!strstr($word, $longest_common_substring[0] . $char)) {
// No match
break 2;
}
}
// we found the current char in each word, so add it to the first longest_common_substring element,
// then start checking again using the next char as well
$longest_common_substring[0].= $char;
}
// We've finished looping through the entire shortest_string.
// Remove the first char and start all over. Do this until there are no more
// chars to search on.
array_shift($shortest_string);
}
// If we made it here then we've run through everything
usort($longest_common_substring, $sort_by_strlen);
return array_pop($longest_common_substring);
}
任何帮助深表感谢.
UPDATE
PHP levenshtein函数限制为255个字符,我正在搜索的一些干草堆是1000个字符.
最佳答案 写这个作为第二个答案,因为它不是基于我以前的(坏)一个.
此代码基于http://en.wikipedia.org/wiki/Wagner%E2%80%93Fischer_algorithm和http://en.wikipedia.org/wiki/Approximate_string_matching#Problem_formulation_and_algorithms
给出$needle,它返回$haystack的一个(可能是几个)最小levenshtein子串.现在,levenshtein距离只是编辑距离的一个衡量标准,它可能实际上并不适合您的需求. ‘hte’在这个指标上更接近’他’而不是”’.我提出的一些例子表明了这种技术的局限性.我相信这比我之前给出的答案要可靠得多,但让我知道它对你有什么用.
// utility function - returns the key of the array minimum
function array_min_key($arr)
{
$min_key = null;
$min = PHP_INT_MAX;
foreach($arr as $k => $v) {
if ($v < $min) {
$min = $v;
$min_key = $k;
}
}
return $min_key;
}
// Calculate the edit distance between two strings
function edit_distance($string1, $string2)
{
$m = strlen($string1);
$n = strlen($string2);
$d = array();
// the distance from '' to substr(string,$i)
for($i=0;$i<=$m;$i++) $d[$i][0] = $i;
for($i=0;$i<=$n;$i++) $d[0][$i] = $i;
// fill-in the edit distance matrix
for($j=1; $j<=$n; $j++)
{
for($i=1; $i<=$m; $i++)
{
// Using, for example, the levenshtein distance as edit distance
list($p_i,$p_j,$cost) = levenshtein_weighting($i,$j,$d,$string1,$string2);
$d[$i][$j] = $d[$p_i][$p_j]+$cost;
}
}
return $d[$m][$n];
}
// Helper function for edit_distance()
function levenshtein_weighting($i,$j,$d,$string1,$string2)
{
// if the two letters are equal, cost is 0
if($string1[$i-1] === $string2[$j-1]) {
return array($i-1,$j-1,0);
}
// cost we assign each operation
$cost['delete'] = 1;
$cost['insert'] = 1;
$cost['substitute'] = 1;
// cost of operation + cost to get to the substring we perform it on
$total_cost['delete'] = $d[$i-1][$j] + $cost['delete'];
$total_cost['insert'] = $d[$i][$j-1] + $cost['insert'];
$total_cost['substitute'] = $d[$i-1][$j-1] + $cost['substitute'];
// return the parent array keys of $d and the operation's cost
$min_key = array_min_key($total_cost);
if ($min_key == 'delete') {
return array($i-1,$j,$cost['delete']);
} elseif($min_key == 'insert') {
return array($i,$j-1,$cost['insert']);
} else {
return array($i-1,$j-1,$cost['substitute']);
}
}
// attempt to find the substring of $haystack most closely matching $needle
function shortest_edit_substring($needle, $haystack)
{
// initialize edit distance matrix
$m = strlen($needle);
$n = strlen($haystack);
$d = array();
for($i=0;$i<=$m;$i++) {
$d[$i][0] = $i;
$backtrace[$i][0] = null;
}
// instead of strlen, we initialize the top row to all 0's
for($i=0;$i<=$n;$i++) {
$d[0][$i] = 0;
$backtrace[0][$i] = null;
}
// same as the edit_distance calculation, but keep track of how we got there
for($j=1; $j<=$n; $j++)
{
for($i=1; $i<=$m; $i++)
{
list($p_i,$p_j,$cost) = levenshtein_weighting($i,$j,$d,$needle,$haystack);
$d[$i][$j] = $d[$p_i][$p_j]+$cost;
$backtrace[$i][$j] = array($p_i,$p_j);
}
}
// now find the minimum at the bottom row
$min_key = array_min_key($d[$m]);
$current = array($m,$min_key);
$parent = $backtrace[$m][$min_key];
// trace up path to the top row
while(! is_null($parent)) {
$current = $parent;
$parent = $backtrace[$current[0]][$current[1]];
}
// and take a substring based on those results
$start = $current[1];
$end = $min_key;
return substr($haystack,$start,$end-$start);
}
// some testing
$data = array( array('foo',' foo'), array('fat','far'), array('dat burn','rugburn'));
$data[] = array('big yellow school bus','they rode the bigyellow schook bus that afternoon');
$data[] = array('bus','they rode the bigyellow schook bus that afternoon');
$data[] = array('big','they rode the bigyellow schook bus that afternoon');
$data[] = array('nook','they rode the bigyellow schook bus that afternoon');
$data[] = array('they','console, controller and games are all in very good condition, only played occasionally. includes power cable, controller charge cable and audio cable. smoke free house. pes 2011 super street fighter');
$data[] = array('controker','console, controller and games are all in very good condition, only played occasionally. includes power cable, controller charge cable and audio cable. smoke free house. pes 2011 super street fighter');
foreach($data as $dat) {
$substring = shortest_edit_substring($dat[0],$dat[1]);
$dist = edit_distance($dat[0],$substring);
printf("Found |%s| in |%s|, matching |%s| with edit distance %d\n",$substring,$dat[1],$dat[0],$dist);
}
