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发表于 2011-10-25 16:35 |只看该作者 |倒序浏览

php 实现KMP算法

<?php
/**
* KMP算法的PHP实现
*
* @author zhaojiangwei 2011/10/22 10:28
*/
Php代码
1.
class KMP{
private $next = NULL; //模式串T的next数组
private $t = NULL; //模式串
private $str = NULL; //主串
public function KMP($str){
$this->str = str_split($str);
$this->next = array();
}
//返回主串的长度
public function getStrCount(){
return count($this->str);
}
//返回结果
public function getStrPos($substr){
$substr = str_split($substr);
$this->getNext($substr);
$strCount = $this->getStrCount();
$substrCount = count($substr);
$subIndex = 0;//子串的起始比较位置
$strIndex = 0;//主串目前的比较到的位置
while($subIndex < $substrCount && ($strCount - $strIndex) >= ($substrCount - $subIndex)){
if($subIndex == -1 || $this->str[$strIndex] == $substr[$subIndex]){
$subIndex ++;
$strIndex ++;
}else{
$subIndex = $this->next[$subIndex];
}
}
if($subIndex == $substrCount){
return $strIndex - $substrCount;
}else{
return false;
}
}
//求模式串的NEXT数组
public function getNext($t){
if(!is_array($t)){
$t = str_split($t);
}
$this->next[0] = -1;
$count = count($t);
$i = 0;
$j = -1;
while($i < $count){
if($j == -1 || $t[$i] == $t[j]){
$j ++;
$i ++;
if($t[$i] == $t[$j]){
$this->next[$i] = $this->next[$j];
}else{
$this->next[$i] = $j;
}
}else{
$j = $this->next[$j];
}
}
return $this->next;
}
}