BMH子串查詢演算法(PHP實現)

嗯哼9925發表於2018-01-07
演算法PHP
程式碼
interface StringSearchable
{
    public function search($substring, $buffer);
}
class BoyerMooreStringSearch implements StringSearchable
{
    public $substring = null;
    public $buffer = “;
    public $jumpTable = array();
    protected $results = array();
    public function __construct()
    {    
        
    }
    public function __destruct()
    {
    }
    public function search($substring, $buffer)
    {    
        $this->results = array();
        $this->substring = $substring;
        $this->buffer = $buffer;
        $this->deriveJumpTable();
        
        $substringLen = strlen($this->substring);
        $currentCharIndex = $substringLen – 1;
        $bufferLen = strlen($this->buffer);
        while ($currentCharIndex < $bufferLen) {    
            for ($i = $substringLen – 1; $i >= 0; $i–) {
                if ($this->buffer[$currentCharIndex – $substringLen + $i + 1] == $this->substring[$i]) {
                    if ($i == 0) {
                        $this->results[] = $currentCharIndex – $substringLen;
                        $currentCharIndex += $this->getJumpLength($this->buffer[$currentCharIndex]);
                    } else {
                        continue;
                    }
                } else {
                    $currentCharIndex += $this->getJumpLength($this->buffer[$currentCharIndex]);
                    break;
                }
            }
        }
        return (sizeof($this->results) > 0);
    }
    
    protected function deriveJumpTable()
    {
        $maxJump = strlen($this->substring);
        for ($i = strlen($this->substring) – 2; $i >= 0; $i–) {
            if (!array_key_exists($this->substring[$i], $this->jumpTable)) {
                $this->jumpTable[$this->substring[$i]]] = $maxJump – $i -1;
            }
        }
    }
    public function getJumpTable()
    {
        return $this->jumpTable;    
    }
    public function getResults()
    {
        return $this->results;
    }
    public function getResultsCount()
    {
        return sizeof($this->results);
    }
    public function getJumpLength($charIndex)
    {
        if (array_key_exists($charIndex, $this->jumpTable)) {
            return $this->jumpTable[$charIndex];
        } else {
            return strlen($this->substring);
        }
    }
}
function Main()
{    
    $poem = <<<POEM
    you son of bitch
    god damn it
    hey,god love me
    POEM;
    $bm = new BoyerMooreStringSearch();
    $bm->search(`god`, $poem);
    $count = $bm->getResultsCount;
    echo $count;
}
複製程式碼
本文轉自Phinecos(洞庭散人)部落格園部落格，原文連結：http://www.cnblogs.com/phinecos/archive/2010/04/21/1717668.html，如需轉載請自行聯絡原作者


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