php 實現KMP演算法

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<?php

    /**

     * KMP演算法的PHP實現

     *

     * @author zhaojiangwei 2011/10/22 10:28

     */

    class KMP{

        private $next = NULL; //模式串T的next數組

        private $t = NULL; //模式串

        private $str = NULL; //主串

        public function KMP($str){

            $this->str = str_split($str);

            $this->next = array();

        }

        //返回主串的長度

        public function getStrCount(){

            return count($this->str);

        }

        //返回結果

        public function getStrPos($substr){

            $substr = str_split($substr);

            $this->getNext($substr);

            $strCount = $this->getStrCount();

            $substrCount = count($substr);

            $subIndex = 0;//子串的起始比較位置

            $strIndex = 0;//主串目前的比較到的位置

            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數組

         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;

        }

   }

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