在PHP中不包含空格的情况下查找两个字符串之间的通用字母的优雅代码是什么?
还返回一个相似度索引，即计算常见字符的数量，并将其返回为字符总数的百分比。
假设我有一个字符串"LEGENDARY"，而另一个字符串是"BARNEY STINSON"，所以我需要找到通用字母b/w，不包括空格。
我的代码也应该返回一个相似度索引，即计数常见字符的数量，并返回作为字符总数的百分比。
对于这两个字符串，常见字符是"ARNEY"，所以分数是5/22 ~= 22%。有什么帮助吗?
我发现要计算字符串之间的相似百分比，Levenshtein和Jaro Winkler算法对拼写错误和字符串之间的小变化很有效，而Smith Waterman Gotoh算法对字符串很有效，其中文本的重要块是相同的，但在边缘有"噪声"。这个类似问题的答案显示了更多的细节。
下面是使用这三个示例返回两个字符串之间相似度百分比的php示例:Levenshtein
echo levenshtein("LEGENDARY","BARNEY STINSON");
Jaro温克勒
class StringCompareJaroWinkler
{
public function compare($str1, $str2)
{
return $this->JaroWinkler($str1, $str2, $PREFIXSCALE = 0.1 );
}
private function getCommonCharacters( $string1, $string2, $allowedDistance ){
$str1_len = mb_strlen($string1);
$str2_len = mb_strlen($string2);
$temp_string2 = $string2;
$commonCharacters='';
for( $i=0; $i < $str1_len; $i++){
$noMatch = True;
// compare if char does match inside given allowedDistance
// and if it does add it to commonCharacters
for( $j= max( 0, $i-$allowedDistance ); $noMatch && $j < min( $i + $allowedDistance + 1, $str2_len ); $j++){
if( $temp_string2[$j] == $string1[$i] ){
$noMatch = False;
$commonCharacters .= $string1[$i];
$temp_string2[$j] = '';
}
}
}
return $commonCharacters;
}
private function Jaro( $string1, $string2 ){
$str1_len = mb_strlen( $string1 );
$str2_len = mb_strlen( $string2 );
// theoretical distance
$distance = (int) floor(min( $str1_len, $str2_len ) / 2.0);
// get common characters
$commons1 = $this->getCommonCharacters( $string1, $string2, $distance );
$commons2 = $this->getCommonCharacters( $string2, $string1, $distance );
if( ($commons1_len = mb_strlen( $commons1 )) == 0) return 0;
if( ($commons2_len = mb_strlen( $commons2 )) == 0) return 0;
// calculate transpositions
$transpositions = 0;
$upperBound = min( $commons1_len, $commons2_len );
for( $i = 0; $i < $upperBound; $i++){
if( $commons1[$i] != $commons2[$i] ) $transpositions++;
}
$transpositions /= 2.0;
// return the Jaro distance
return ($commons1_len/($str1_len) + $commons2_len/($str2_len) + ($commons1_len - $transpositions)/($commons1_len)) / 3.0;
}
private function getPrefixLength( $string1, $string2, $MINPREFIXLENGTH = 4 ){
$n = min( array( $MINPREFIXLENGTH, mb_strlen($string1), mb_strlen($string2) ) );
for($i = 0; $i < $n; $i++){
if( $string1[$i] != $string2[$i] ){
// return index of first occurrence of different characters
return $i;
}
}
// first n characters are the same
return $n;
}
private function JaroWinkler($string1, $string2, $PREFIXSCALE = 0.1 ){
$JaroDistance = $this->Jaro( $string1, $string2 );
$prefixLength = $this->getPrefixLength( $string1, $string2 );
return $JaroDistance + $prefixLength * $PREFIXSCALE * (1.0 - $JaroDistance);
}
}
$jw = new StringCompareJaroWinkler();
echo $jw->compare("LEGENDARY","BARNEY STINSON");
Smith Waterman Gotoh
class SmithWatermanGotoh
{
private $gapValue;
private $substitution;
/**
* Constructs a new Smith Waterman metric.
*
* @param gapValue
* a non-positive gap penalty
* @param substitution
* a substitution function
*/
public function __construct($gapValue=-0.5,
$substitution=null)
{
if($gapValue > 0.0) throw new Exception("gapValue must be <= 0");
//if(empty($substitution)) throw new Exception("substitution is required");
if (empty($substitution)) $this->substitution = new SmithWatermanMatchMismatch(1.0, -2.0);
else $this->substitution = $substitution;
$this->gapValue = $gapValue;
}
public function compare($a, $b)
{
if (empty($a) && empty($b)) {
return 1.0;
}
if (empty($a) || empty($b)) {
return 0.0;
}
$maxDistance = min(mb_strlen($a), mb_strlen($b))
* max($this->substitution->max(), $this->gapValue);
return $this->smithWatermanGotoh($a, $b) / $maxDistance;
}
private function smithWatermanGotoh($s, $t)
{
$v0 = [];
$v1 = [];
$t_len = mb_strlen($t);
$max = $v0[0] = max(0, $this->gapValue, $this->substitution->compare($s, 0, $t, 0));
for ($j = 1; $j < $t_len; $j++) {
$v0[$j] = max(0, $v0[$j - 1] + $this->gapValue,
$this->substitution->compare($s, 0, $t, $j));
$max = max($max, $v0[$j]);
}
// Find max
for ($i = 1; $i < mb_strlen($s); $i++) {
$v1[0] = max(0, $v0[0] + $this->gapValue, $this->substitution->compare($s, $i, $t, 0));
$max = max($max, $v1[0]);
for ($j = 1; $j < $t_len; $j++) {
$v1[$j] = max(0, $v0[$j] + $this->gapValue, $v1[$j - 1] + $this->gapValue,
$v0[$j - 1] + $this->substitution->compare($s, $i, $t, $j));
$max = max($max, $v1[$j]);
}
for ($j = 0; $j < $t_len; $j++) {
$v0[$j] = $v1[$j];
}
}
return $max;
}
}
class SmithWatermanMatchMismatch
{
private $matchValue;
private $mismatchValue;
/**
* Constructs a new match-mismatch substitution function. When two
* characters are equal a score of <code>matchValue</code> is assigned. In
* case of a mismatch a score of <code>mismatchValue</code>. The
* <code>matchValue</code> must be strictly greater then
* <code>mismatchValue</code>
*
* @param matchValue
* value when characters are equal
* @param mismatchValue
* value when characters are not equal
*/
public function __construct($matchValue, $mismatchValue) {
if($matchValue <= $mismatchValue) throw new Exception("matchValue must be > matchValue");
$this->matchValue = $matchValue;
$this->mismatchValue = $mismatchValue;
}
public function compare($a, $aIndex, $b, $bIndex) {
return ($a[$aIndex] === $b[$bIndex] ? $this->matchValue
: $this->mismatchValue);
}
public function max() {
return $this->matchValue;
}
public function min() {
return $this->mismatchValue;
}
}
$o = new SmithWatermanGotoh();
echo $o->compare("LEGENDARY","BARNEY STINSON");
参见similar_text()。如果你想要排除空格，简单的str_replace(' ', '', $string);优先。
echo similar_text ( 'LEGENDARY' , 'BARNEYSTINSON', $percent); // outputs 3
echo $percent; // outputs 27.272727272727
这是另一种使用唯一字符
的方法<?php
function unique_chars($string) {
return count_chars(strtolower(str_replace(' ', '', $string)), 3);
}
function compare_strings($a, $b) {
$index = similar_text(unique_chars($a), unique_chars($b), $percent);
return array('index' => $index, 'percent' => $percent);
}
print_r( compare_strings('LEGENDARY', 'BARNEY STINSON') );
// outputs:
?>
Array
(
[index] => 5
[percent] => 55.555555555556
)