今天有网友出了道题：
给出如下的父子结构（你可以用你所用语言的类似结构来描述，第一列是父，第二列是子），将其梳理成类似如图的层次父子结构。
origin = [('A112', 'A1122'),
('A', 'A1'),
('A', 'A2'),
('A1', 'A11'),
('A2', 'A21'),
('A2', 'A22'),
('A', 'A3'),
('A22', 'A221'),
('A11', 'A111'),
('A21', 'A211'),
('A11', 'A112'),
('A21', 'A212'),
('A11', 'A113'),
('A112', 'A1121'),
('A3', 'A31'),
('A31', 'A311'),
('A22', 'A222'),
('A31', 'A312'),
('A31', 'A313'),
('A311', 'A3111'),
('A312', 'A3121'),
('A3111', 'A31111')]
输出结果：
看了一下是无限级分类的原理，可以用递归来实现：
<?php
$origin = [
['A112', 'A1122'],
['A', 'A1'],
['A', 'A2'],
['A1', 'A11'],
['A2', 'A21'],
['A2', 'A22'],
['A', 'A3'],
['A22', 'A221'],
['A11', 'A111'],
['A21', 'A211'],
['A11', 'A112'],
['A21', 'A212'],
['A11', 'A113'],
['A112', 'A1121'],
['A3', 'A31'],
['A31', 'A311'],
['A22', 'A222'],
['A31', 'A312'],
['A31', 'A313'],
['A311', 'A3111'],
['A312', 'A3121'],
['A3111', 'A31111']
]; // 根据父id找出子信息
function level($cate, $html = '-', $pid = '0', $level = 0) {
$arr = array();
foreach($cate as $val) {
if($val[0] == $pid) {
$val['level'] = $level + 1;
$val['html'] = str_repeat($html, $level);
$arr[] = $val;
$arr = array_merge($arr, level($cate, $html, $val[1], $level + 1));
}
}
return $arr;
} // 构建*分类
$pids = [];
$cids = [];
foreach($origin as $val) {
$pids[] = $val[0];
$cids[] = $val[1];
}
$top = array_flip(array_diff($pids, $cids));
foreach($top as $key => $val) {
$origin[] = ['0', $key];
} $res = level($origin, ' ');
foreach($res as $k => $v) {
echo $v['html'],$v[1],PHP_EOL;
}
输出：