php简单中文分词系统(1/2)_PHP教程

php简单中文分词系统结构：首字散列表、Trie索引树结点优点：分词中，不需预知待查询词的长度，沿树链逐字匹配。缺点：构造和维护比较复杂，单词树枝多，浪费了一定的空间

php教程简单中文分词系统

结构：首字散列表、trie索引树结点
优点：分词中，不需预知待查询词的长度，沿树链逐字匹配。
缺点：构造和维护比较复杂，单词树枝多，浪费了一定的空间
* @version 0.1
* @todo 构造通用的字典算法，并写了一个简易的分词
* @author [e-mail]
* trie字典树
*
*/

class trie
{
private $trie;

function __construct()
{
$trie = array('children' => array(),'isword'=>false);
}

/**
* 把词加入词典
*
* @param string $key
*/
function &setword($word='')
{
$trienode = &$this->trie;
for($i = 0;$i {
$character = $word[$i];
if(!isset($trienode['children'][$character]))
{
$trienode['children'][$character] = array('isword'=>false);
}
if($i == strlen($word)-1)
{
$trienode['children'][$character] = array('isword'=>true);
}
$trienode = &$trienode['children'][$character];
}
}

/**
* 判断是否为词典词
*
* @param string $word
* @return bool true/false
*/
function & isword($word)
{
$trienode = &$this->trie;
for($i = 0;$i {
$character = $word[$i];
if(!isset($trienode['children'][$character]))
{
return false;
}
else
{
//判断词结束
if($i == (strlen($word)-1) && $trienode['children'][$character]['isword'] == true)
{
return true;
}
elseif($i == (strlen($word)-1) && $trienode['children'][$character]['isword'] == false)
{
return false;
}
$trienode = &$trienode['children'][$character];
}
}
}

/**
* 在文本$text找词出现的位置
*
* @param string $text
* @return array array('position'=>$position,'word' =>$word);
*/
function search($text="")
{
$textlen = strlen($text);
$trienode = $tree = $this->trie;
$find = array();
$wordrootposition = 0;//词根位置
$prenode = false;//回溯参数,当词典ab,在字符串aab中，需要把$i向前回溯一次
$word = '';
for ($i = 0; $i {

if(isset($trienode['children'][$text[$i]]))
{
$word = $word .$text[$i];
$trienode = $trienode['children'][$text[$i]];
if($prenode == false)
{
$wordrootposition = $i;
}
$prenode = true;
if($trienode['isword'])
{
$find[] = array('position'=>$wordrootposition,'word' =>$word);
}
}
else
{
$trienode = $tree;
$word = '';
if($prenode)
{
$i = $i -1;
$prenode = false;
}
}
}
return $find;
}
}

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