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前些日子和一些朋友讨论关于无限分类的算法问题，其中提到了利用php数组进行操作的想法。其实无限分类算法就是树的算法。
利用数据库存储数据加递归搜索似乎是目前很流行的一种方法，但这种方法的效率低下，并增加了不少数据库的负担。
我这个算法采用文本方式存储数据，效率应该还可以。由于时间关系，算法是匆匆完成没有经过严格测试就放上来了，大家有兴趣的话就测试一下，找找其中的bug，或改善一下算法的性能。
提醒一点，如果你的php可利用的内存不到1g，请不要尝试去创建一个具有100万个节点的树。。。:lol:
树的操作算法是各种高级数据结构算法的基础，估计不少同学在大学的时候都学烂了，所以我就不必细讲了。现在要讨论的是如何在php这个编程环境里面如果实现该算法最大的性能。
好吧，我来抛砖引玉。
因时间关系没有写注释，看不懂的同学可以提问。
[php]
<?php
/**
* 树操作类
*
* 利用php数组对树进行构造，删除和遍历等操作，全部遍历采用非递归方法实现，并实现iterator和countable操作。
* 该算法可适用与无限分类等相关领域，对于同时操作百万级以上的数据可能需要512m以上的内存支持。
* 利用文本存储数据结构，如果需要数据库存储可继承本类并覆盖loadtree和savetree方法。
*
* @copyrihgt sentrychen@hotmail.com, 2008
* @author sentrychen sentrychen@hotmail.com>
* @version $id: tree.php, v 0.0.1 2008/10/01 11:51:25 uw exp $
*/
class itc_tree implements iterator,countable
{
const id = 'i';
const pid = 'p';
const level ='l';
const data = 'd';
const children = 'c';
const dfs = 'dfs';
const bfs = 'bfs';
protected $_tree = array();
protected $_filename = '';
protected $_prefix = 'tree_';
protected $_path = '';
protected $_rootid = 0;
protected $_lastid = 0;
protected $_way = self::dfs;
protected $_stack = array();
public function __construct($name, $path = '')
{
$this->loadtree($name, $path);
}
public function loadtree ($name, $path = '')
{
if ($path != '') {
if (is_dir($path)) {
$this->_path = rtrim($path, '/\\') . directory_separator;
} else {
die('no such directory :' . $path);
}
}
$name = md5($name);
$this->_filename = $this->_path . $this->_prefix . $name ;
if (is_file($this->_filename)) {
$this->_tree = json_decode(file_get_contents($this->_filename),true);
$this->_inittree();
return true;
}
return false;
}
protected function _inittree ()
{
$ary = $this->listtotree($this->_tree);
$this->_rootid = $ary['topid'];
$this->_lastid = $ary['lastid'];
$this->_tree[$this->_rootid][self::level] = 1;
return $this;
}
public function listtotree(&$list){
$return = array('topid'=>0,'lastid'=>0);
foreach ($list as $id => &$node){
if (isset($list[$node[self::pid]]))
$list[$node[self::pid]][self::children][$id] = &$node;
else
$return['topid'] = $id;
if ($id > $return['lastid']) $return['lastid'] = $id;
}
return $return;
}
public function settreebylist (array $list)
{
if (!$this->_checklist($list)){
die('incorrect data format');
}
$this->_tree = $list;
$this->_inittree();
return true;
}
public function gettree($id = null)
{
if (null === $id) $id = $this->_rootid;
if (isset($this->_tree[$id]))
return $this->_tree[$id];
else
return null;
}
public function getparent($id){
if (isset($this->_tree[$id]) && isset($this->_tree[$this->_tree[$id][self::parent]])){
return $this->_tree[$this->_tree[$id][self::parent]];
}
return null;
}
public function getparentsid($start,$level = null)
{
$parent = array();
$id = $start;
do{
if (!isset($this->_tree[$id])) break;
$pid = $this->_tree[$id][self::pid];
if (null !== $level && !$level--) break;
if (!isset($this->_tree[$pid])) break;
}
while(true);
return $parent;
}
public function getchildren($id){
if (isset($this->_tree[$id])){
return $this->_tree[$id][self::children];
}
return null;
}
public function gettreeall()
{
return $this->_tree;
}
public function gettreelist()
{
if (isset($this->_tree)) {
return $this->tolist($this->_tree);
}
return null;
}
public function tolist($tree){
$ary = array();
foreach ($tree as $id => $node){
unset($node[self::children]);
$ary[$id] = $node;
}
return $ary;
}
public function getdepth(){
$depth = 1;
$id = $this->_rootid;
$stack = array($id);
$i = 0;
if (!isset($this->_tree[$id][self::level]))
$this->_tree[$id][self::level] = 1;
do{
$id = $stack[$i++];
$pid = $this->_tree[$id][self::pid];
if (isset($this->_tree[$id][self::children])){
$stack = array_merge($stack,array_keys($this->_tree[$id][self::children]));
}
if (isset($this->_tree[$id][self::level])){
$level = $this->_tree[$id][self::level];
}
else {
$level = $this->_tree[$pid][self::level] + 1;
$this->_tree[$id][self::level] = $level;
}
if ($depth < $level) $depth = $level;
}while(isset($stack[$i]));
return $depth;
}
public function getlastid(){
return $this->_lastid;
}
public function getrootid(){
return $this->_rootid;
}
public function getroot(){
return $this->_tree[$this->_rootid];
}
public function getdata($id){
if (isset($this->_tree[$id])){
return $this->_tree[$id][self::data];
}
return null;
}
public function setdata($id,$data){
if (isset($this->_tree[$id])){
$this->_tree[$id][self::data] = $data;
return true;
}
return false;
}
public function addroot($data = null)
{
$root = array(
self::id => $this->_rootid,
self::pid => $this->_rootid - 1,
self::level => 1,
self::data => $data
);
$this->_tree[$this->_rootid] = &$root;
$this->_lastid = $this->_rootid;
return $this->_rootid;
}
public function addleaf($pid,$data = null)
{
if (!isset($this->_tree[$pid])){
if (isset($this->_tree[$this->_rootid]))
$pid = $this->_rootid;
else {
$this->_lastid = $this->addroot($data);
return $this->_lastid;
}
}
$id = ++$this->_lastid;
$level = isset($this->_tree[$pid][self::level])? $this->_tree[$pid][self::level] + 1 : null;
$this->_tree[$id] = array(
self::id => $id,
self::pid => $pid,
self::level => $level,
self::data => $data
);
$this->_tree[$pid][self::children][$id] = &$this->_tree[$id];
return $id;
}
public function insertchild($pid, $children)
{
if (!isset($this->_tree[$pid])){
return false;
}
if ($children instanceof self){
$children = $children->gettree();
}
if (is_array($children)){
$children = $this->tolist($children);
$lastid = $this->_lastid + 1;
$list = array();
foreach ($children as $id => $node){
$node[self::id] +=$lastid;
$node[self::pid] +=$lastid;
$list[$id + $lastid] = $node;
}
$ary = $this->listtotree($list);
$this->_lastid = $ary['lastid'];
$list[$ary['topid']][self::pid] = $pid;
$this->_tree += $list;
$this->_tree[$pid][self::children][$ary['topid']] = &$this->_tree[$ary['topid']];
return $this->_lastid;
}
return $this->addleaf($pid,$children);
}
public function deletechild($id){
if (!isset($this->_tree[$id])){
return null;
}
$pid = $this->_tree[$id][self::pid];
$deltree = array();
if (isset($this->_tree[$pid])){
unset($this->_tree[$pid][self::children][$id]);
}
$stack = array($id);
do{
$id = array_pop($stack);
if (isset($this->_tree[$id][self::children]))
$stack =array_merge($stack, array_keys($this->_tree[$id][self::children]));
$deltree[$id] = $this->_tree[$id];
unset($this->_tree[$id]);
}while(!empty($stack));
return $deltree;
}
public function emptytree(){
$this->_tree = array();
$this->_rootid = 0;
$this->_lastid = 0;
return true;
}
public function destroytree(){
$this->emptytree();
if (is_file($this->_filename))
unlink($this->_filename);
return true;
}
protected function _checklist (array $list)
{
$ischecked = true;
$topnum = 0;
foreach ($list as $id => $node) {
if (! isset($node[self::id]) || ! isset($node[self::pid]) || $node[self::id] != $id) {
$ischecked = false;
break;
}else{
if (!isset($list[$node[self::pid]])) $topnum++;
if ($topnum > 1){
$ischecked = false;
break;
}
}
}
return $ischecked;
}
public function getlevel($id){
if (isset($this->_tree[$id]) && isset($this->_tree[$id][self::level]) )
return $this->_tree[$id][self::level];
$level = 0;
$id2 = $id;
while(isset($this->_tree[$id2])){
if (isset($this->_tree[$id2][self::level])){
$level += $this->_tree[$id2][self::level];
break;
}
$level++;
$id2 = $this->_tree[$id2][self::pid];
}
if (isset($this->_tree[$id]))
$this->_tree[$id][self::level] = $level;
return $level;
}
public function dfs($callback = null,$id = null){
if (null === $id) $id = $this->_rootid;
if (!isset($this->_tree[$id])){
return null;
}
if (null == $callback || !function_exists($callback)){
return null;
}
$stack = array($id);
$return = null;
do{
$id = array_shift($stack);
$children = null;
if (isset($this->_tree[$id][self::children])){
$children = array_keys($this->_tree[$id][self::children]);
$stack = array_merge($children,$stack);
}
$args = array(
self::id => $id,
self::pid => $this->_tree[$id][self::pid],
self::data => &$this->_tree[$id][self::data],
self::level => $this->getlevel($id),
self::children => $children
);
$back = call_user_func($callback,$args);
if (isset($back)){
if (is_string($back)) $return .= $back;
else if (is_array($back)) $return[] = $back;
else if (is_int($back)) $return += $back;
else if (is_bool($back) && $back) $return = $this->_tree[$id];
}
}while(!empty($stack));
return $return;
}
public function bfs($callback = null,$id = null){
if (null === $id) $id = $this->_rootid;
if (!isset($this->_tree[$id])){
return array();
}
if (null == $callback || !function_exists($callback)){
$callback = null;
}
$stack = array($id);
$return = null;
do{
$id = array_shift($stack);
$children = null;
if (isset($this->_tree[$id][self::children])){
$children = array_keys($this->_tree[$id][self::children]);
$stack = array_merge($stack,$children);
}
$args = array(
self::id => $id,
self::pid => $this->_tree[$id][self::pid],
self::data => &$this->_tree[$id][self::data],
self::level => $this->getlevel($id),
self::children => $children
);
$return = call_user_func($callback,$args);
if (isset($back)){
if (is_string($back)) $return .= $back;
else if (is_array($back)) $return[] = $back;
else if (is_int($back)) $return += $back;
else if (is_bool($back) && $back) $return = $this->_tree[$id];
}
}while(!empty($stack));
return $return;
}
public function savetree(){
file_put_contents($this->_filename, json_encode($this->tolist($this->_tree)));
return true;
}
public function setway($way = self::dfs){
if (in_array($way,array(self::dfs,self::bfs))){
$this->_way = $way;
$this->rewind();
}
return $this;
}
public function rewind()
{
if (isset($this->_tree[$this->_rootid]))
{
$this->_stack = array($this->_rootid);
}
else{
$this->_stack = array();
}
return $this;
}
public function next()
{
$id = array_shift($this->_stack);
if (isset($this->_tree[$id][self::children])){
$children = array_keys($this->_tree[$id][self::children]);
if ($this->_way == self::bfs)
$this->_stack = array_merge($this->_stack,$children);
else
$this->_stack = array_merge($children,$this->_stack);
}
}
public function count()
{
return count($this->_tree);
}
public function key()
{
return current($this->_stack);
}
public function current()
{
$id = current($this->_stack);
if (isset($this->_tree[$id])){
return $this->_tree[$id];
}
else
return null;
}
public function valid()
{
return !empty($this->_stack);
}
}
[/php]
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