Nine lines of code is too wasteful, and five lines of code are sufficient. you do not need to recursively format the tree of infinitely classified data.

Nine lines of code is too wasteful, and five lines of code are sufficient. you do not need to recursively format the tree of infinitely classified data.

We know that the infinite classification of many open-source software uses recursive algorithms, but we know that recursion is a waste of time and space (memory ), Last time I also shared my original method of generating tree with unlimited categories. a enthusiastic php expert gave me valuable suggestions. I tested it, this code takes a very short time. for details, refer. The code is also very concise. /** * This method is provided by @ Tonton * Http://my.oschina.net/u/918697 * @ Date 2012-12-12 */ Function genTree5 ($ items ){ Foreach ($ items as $ item) $ Items [$ item ['pid '] ['son'] [$ item ['id'] = & $ items [$ item ['id']; Return isset ($ items [0] ['son'])? $ Items [0] ['son']: array (); } /** * Format the data into a tree structure. * @ Author Xuefen. Tong * @ Param array $ items * @ Return array */ Function genTree9 ($ items ){ $ Tree = array (); // formatted tree Foreach ($ items as $ item) If (isset ($ items [$ item ['pid ']) $ Items [$ item ['pid '] ['son'] [] = & $ items [$ item ['id']; Else $ Tree [] = & $ items [$ item ['id']; Return $ tree; } $ Items = array ( 1 => array ('id' => 1, 'pid '=> 0, 'name' => 'jiangxi '), 2 => array ('id' => 2, 'pid '=> 0, 'name' => 'heilongjiang province '), 3 => array ('id' => 3, 'pid '=> 1, 'name' => 'nanchang city '), 4 => array ('id' => 4, 'pid '=> 2, 'name' => 'Harbin '), 5 => array ('id' => 5, 'pid '=> 2, 'name' => 'jixi city '), 6 => array ('id' => 6, 'pid '=> 4, 'name' => 'xiangfang region '), 7 => array ('id' => 7, 'pid '=> 4, 'name' => 'nangang '), 8 => array ('id' => 8, 'pid '=> 6, 'name' =>' and Xinglu '), 9 => array ('id' => 9, 'pid '=> 7, 'name' => 'westbrook street '), 10 => array ('id' => 10, 'pid '=> 8, 'name' => 'Northeast forestry Emy '), 11 => array ('id' => 11, 'pid '=> 9, 'name' => 'Harbin Institute of Technology '), 12 => array ('id' => 12, 'pid '=> 8, 'name' => 'Harbin Normal University '), 13 => array ('id' => 13, 'pid '=> 1, 'name' => 'ganzhou city '), 14 => array ('id' => 14, 'pid '=> 13, 'name' => 'ganxian '), 15 => array ('id' => 15, 'pid '=> 13, 'name' => 'yudu County '), 16 => array ('id' => 16, 'pid '=> 14, 'name' => 'moudian Zhen '), 17 => array ('id' => 17, 'pid' => 14, 'name' => 'tagname '), 18 => array ('id' => 18, 'pid '=> 16, 'name' => 'yiyuan cune '), 19 => array ('id' => 19, 'pid '=> 16, 'name' => 'shangba cune '), ); Echo" "; Print_r (genTree5 ($ items )); Print_r (genTree9 ($ items )); // The latter output format. the former format is similar, but the array key values are different, but the data structure is not affected. /* Array ( [0] => Array ( [Id] => 1 [Pid] => 0 [Name] => Jiangxi [Son] => Array ( [0] => Array ( [Id] => 3 [Pid] => 1 [Name] => Nanchang City ) [1] => Array ( [Id] => 13 [Pid] => 1 [Name] => Ganzhou City [Son] => Array ( [0] => Array ( [Id] => 14 [Pid] => 13 [Name] => Ganxian County [Son] => Array ( [0] => Array ( [Id] => 16 [Pid] => 14 [Name] => moudian town [Son] => Array ( [0] => Array ( [Id] => 18 [Pid] => 16 [Name] => Yiyuan village ) [1] => Array ( [Id] => 19 [Pid] => 16 [Name] => Shangba village ) ) ) [1] => Array ( [Id] => 17 [Pid] => 14 [Name] => Datian Township ) ) ) [1] => Array ( [Id] => 15 [Pid] => 13 [Name] => Yudu County ) ) ) ) ) [1] => Array ( [Id] => 2 [Pid] => 0 [Name] => Heilongjiang province [Son] => Array ( [0] => Array ( [Id] => 4 [Pid] => 2 [Name] => Harbin [Son] => Array ( [0] => Array ( [Id] => 6 [Pid] => 4 [Name] => Xiangfang District [Son] => Array ( [0] => Array ( [Id] => 8 [Pid] => 6 [Name] => hexinglu [Son] => Array ( [0] => Array ( [Id] => 10 [Pid] => 8 [Name] => Northeast Forestry University ) [1] => Array ( [Id] => 12 [Pid] => 8 [Name] => Harbin Normal University ) ) ) ) ) [1] => Array ( [Id] => 7 [Pid] => 4 [Name] => Nangang District [Son] => Array ( [0] => Array ( [Id] => 9 [Pid] => 7 [Name] => westbound street [Son] => Array ( [0] => Array ( [Id] => 11 [Pid] => 9 [Name] => Harbin Institute of Technology ) ) ) ) ) ) ) [1] => Array ( [Id] => 5 [Pid] => 2 [Name] => Jixi city ) ) ) )*/