php兑现KMP算法

php兑现KMP算法

php 实现KMP算法
    /**
     * KMP算法的PHP实现
     *
     * @author zhaojiangwei 2011/10/22 10:28
     */

    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;
        }

   }