實現樹狀結構的兩種方法
1。遞歸法
遞歸是指在函數中明確的呼叫它本身。
利用遞歸法實現樹狀結構的特徵是寫入資料速度較快，顯示速度較慢（在樹的分支/層次較多的情況下尤其明顯）。適用與寫入資料量大，樹的結構複雜的情況下。
資料結構(以mysql為例)
程式碼:------------------------------- -------------------------------------------------
CREATE TABLE `tree1` (
`id` tinyint(3) unsigned NOT NULL auto_increment,
`parentid` tinyint(3) unsigned NOTULL Ndefault's
KEY `parentid` (`parentid`)
) TYPE=MyISAM;
(1,0,'樹1'),
(2,0,'樹2'),
(3,0,'樹3' ),
(4,2,'樹2-1'),
(5,4,'樹2-1-1'),
(6,2,'樹2-2' ),
(7,1,'樹1-1'),
(8,1,'樹1-2'),
(9,1,'樹1-3'),
(10,8,'樹1-2-1'),
(11,7,'樹1-1-1'),
(12,11,'樹1-1- 1-1');
----------------------------------------- ---------------------------------------
欄位說明
id,記錄的id號
parentid,記錄的父記錄id（為0則為根記錄）
topic,記錄的顯示標題
顯示程式
順序樹:
PHP代碼:-------------------------------------- ------------------------------------------
/* 資料庫連線*/
mysql_connect();
mysql_select_db('tree');
/* 樹狀顯示的遞歸函數*/
function tree($parentid = 0) {
/*執行sql查詢，取得記錄的標題和id*/
$sql = "select topic,id from tree1 where parentid = $parentid order by id asc";
where parentid = $parentid order by id asc";
= mysql_query($sql);
/* 縮排*/
echo("");
");
while($ra = mysql_fetch_row($rs)) { echo('
/* 遞歸給*/
/* 遞歸給*/
🎜> }
echo("
}
tree();
?>
------------ -------------------------------------------------- ------------------
逆序樹:
PHP代碼:----------- -------------------------------------------------- -------------------
/* 資料庫連線*/
mysql_connect();
mysql_select_db('tree ');
/* 樹狀顯示的遞歸函數*/
function tree($parentid = 0) {
/*執行sql查詢，取得記錄的標題和id*/
$sql = "select topic,id from tree1 where parentid = $parentid order by id desc";
$rs = mysql_query($sql);
/* 縮排*/");
while($ra = mysql_fetch_row($rs)) {
/* 顯示記錄標題*/
/* 顯示記錄標題*/
/* 顯示記錄標題*/
li>');
/* 遞歸呼叫*/
tree($ra[1]);
}
🎜> tree();
?>
----------------------------------- ---------------------------------------------
插入資料程式
PHP代碼:---------------------------------- ----------------------------------------------
/* 資料庫連線*/
mysql_connect();
mysql_select_db('tree');
$sql = "insert into tree (topic,parentid) values('33 -1',3);";
mysql_query($sql);
?>
--------------------- -------------------------------------------------- ---------
2。排序字段法
此方法是透過在資料結構中增加一個標誌記錄在整個樹中的順序位置的字段來實現的。特點是顯示速度和效率高。但在單一樹的結構複雜的情況下，資料寫入效率不足。而且順序排列時候，插入，刪除記錄的演算法過於複雜，故通常用逆序排列。
資料結構(以mysql為例)
程式碼:---------------------------- -------------------------------------------------- --
CREATE TABLE `tree2` (
`id` tinyint(3) unsigned NOT NULL auto_increment,
`parentid` tinyint(3) unsigned NOT N N NM NLDL如何tinyint(3) unsigned NOT NULL default '0',
`layer` tinyint(3) unsigned NOT NULL default '0',
`orders` tinyint(3) unsigned NOT NULL ault ' > `topic` varchar(50) default NULL,
PRIMARY KEY (`id`),
KEY `parentid` (`parentid`),
KEY `parentid` (`parentid`),
KEY `parentid` (`parentid`),
KEY `parentid` (`parentid`),
KEY ``id``(`rootEY)(`YyKEY？ ) TYPE=MyISAM
INSERT INTO `tree2` (`id`, `parentid`, `rootid`, `layer`, `orders`, `topic`) VALUES
,0,0,'樹1'),
(2,0,2,0,0,'樹2'),
(3,0,3,0,0,'樹3') ,
(4,2,2,1,2,'樹2-1'),
(5,4,2,2,3,'樹2-1-1'),
(6,2,2,1,1,'樹2-2'),
(7,1,1,1,4,'樹1-1'),
(8,1,1 ,1,2,'樹1-2'),
(9,1,1,1,1,'樹1-3'),
(10,8,1,2,3,'樹1-2-1'),
(11,7,1,2,5,'樹1-1-1'),
(12,11,1,3,6,'樹1 -1-1-1');
-------------------------------------- ------------------------------------------
顯示程式
PHP代碼：-------------------------------------- ------------------------------------------
/* 資料庫連線*/
mysql_connect();
mysql_select_db('tree');
/* 選取所有根記錄id */
sql = "select id from tree2 where parentid = 0 order by id desc";
$rs = mysql_query($sql);
echo("");
");
$lay = 0;
while( $ra = mysql_fetch_row($rs)) {
echo("");
");
/* 選取此樹所有記錄，並依orders欄位排序*/
$ ,layer from tree2 where rootid = $ra[0] order by orders";
$rs1 = mysql_query($sql);
while($ra1 = mysql_fetch_row($rs1)) { if($ra1[1]>$lay) {
echo(str_repeat("",$ra1[1]-$layse); ra1[1] echo(str_repeat("
",$lay-$ra1[1]));
//echo("$ra1[1]>$lay");
echo("
$lay = $ra1[🎜> $lay = $ra1[1];
}
echo("
}
echo("
?>
------ -------------------------------------------------- ------------------------
插入資料程式
PHP代碼:----- -------------------------------------------------- -------------------------
/* 資料庫連線*/
mysql_connect();
mysql_select_db('tree');
/* 插入根記錄*/
$sql = "insert into tree2 (topic) values ('樹5')";
mysql_query($ sql);
$sql = "update tree2 set rootid = id where id = ".mysql_insert_id();
mysql_query($sql);
/* 插入子記錄*/
$parentid = 5;//父記錄id
/* 取出根記錄id,父記錄縮排層次,父記錄順序位置*/
$sql = "select rootid,layer,orders from tree2 where id = $parentid";
list($rootid,$layer,$orders) = mysql_fetch_row(mysql_query($sql));
/* 更新插入位置後記錄的orders值*/
$sql = " update tree2 set orders = orders 1 where orders > $orders";
mysql_query($sql);
/* 插入記錄*/
$sql = "insert into tree2 (rootid,parentid,orders,layerid,orders,layerid,orders,layerid,orders,layerid,orders,layerid,orders. ,topic) values ($rootid,$parentid,".($orders 1).",".($layer 1).",'樹2-1-1-2')";
mysql_query($ sql);?>
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