如何对多列进行快速排序
我正在寻找快速排序 php 中的一些对象。
我正在对一个对象数组进行排序,
$object->x;
$object->y;
$object->z;
我想首先按 x 排序,然后按 y 排序,然后按 z 排序。
这是我的快速排序功能 它接受一个作业对象数组,并按特定的排序键(x、y 或 z 列)进行排序 该函数返回一个已排序的对象数组,这些对象已按排序键排序。
private function quicksort($objects, $sortKey) {
if(count($objects) < 2) return $objects;
$left = $right = array();
reset($objects);
$pivot_key = key($objects);
$pivot = array_shift($objects);
foreach($objects as $k => $v) {
if($v->$sortKey < $pivot->$sortKey)
$left[$k] = $v;
else
$right[$k] = $v;
}
return array_merge($this->quicksort($left,$sortKey), array($pivot_key => $pivot), $this->quicksort($right,$sortKey));
}
我可以使用快速排序递归算法轻松地对任何单独的列进行快速排序,但是将它们分组在一起然后对这些子组进行第 n 次排序确实让我很困惑。
有我可以查看的算法吗?
I'm looking to quicksort some objects in php.
i'm sorting an array of OBJECTS
$object->x;
$object->y;
$object->z;
I want to first sort by x, then y, then z.
This is my quicksort function
Where it accepts an array of jobjects, and sorts by a particular sortkey (x, y, or z column)
The function returns a sorted array of objects, that have been sorted by the sortkey.
private function quicksort($objects, $sortKey) {
if(count($objects) < 2) return $objects;
$left = $right = array();
reset($objects);
$pivot_key = key($objects);
$pivot = array_shift($objects);
foreach($objects as $k => $v) {
if($v->$sortKey < $pivot->$sortKey)
$left[$k] = $v;
else
$right[$k] = $v;
}
return array_merge($this->quicksort($left,$sortKey), array($pivot_key => $pivot), $this->quicksort($right,$sortKey));
}
I can easily quicksort any individual column using a quicksort recursive algorithm, but grouping them together and then sorting those subgroups to the nth time is really messing with my head.
Is there an algorithm that I could be looking at?
如果你对这篇内容有疑问,欢迎到本站社区发帖提问 参与讨论,获取更多帮助,或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱,如果其他用户或者作者回复了您的评论,将不能在第一时间通知您!
发布评论
评论(3)
您需要采用与最初想法不同的方法。不要递归排序,只进行一次排序,以排序的方式一次考虑所有您的标准(即,如果 x 相同,则测试 y,等等在)。
其他人已经指出了以比较函数作为参数的排序函数。比较函数给定两个对象,并返回哪个对象比另一个对象更小/更大。
在您发布的代码中,您有这样的比较:
而不是测试 $v->$sortKey < $pivot->$sortKey,您需要调用自己的比较函数,例如
在函数
smaller()
中,您定义规则。... 等等。正如你所看到的,排序将确保根据x排序,并且在x相同(不更小,不更大)的情况下继续根据y排序。
You need a different approach than your initial thought. Instead of sorting recursively, do only one sort that takes all your criteria into mind at once, in a ranked fashion (i.e. if x is same, test for y, and so on).
Others have already pointed to sorting functions that take a such called comparison function as an argument. The comparison function is given two of your objects and returns which object is smaller/greater than the other.
In the code you posted, you have this comparison:
Instead of the test $v->$sortKey < $pivot->$sortKey, you need a call to your own comparison function, e.g.
In the function
smaller()
, you define your rules.... and so on. As you can see, the sorting will ensure ordering according to x, and in the case that x is same (not smaller, not greater) continue to order according to y.
您正在实施自己的排序吗?您检查过 https://www.php.net/usort 吗?
usort() 可以接受比较函数,因此您几乎可以实现任何您想要的排序规则。
Are you implementing your own sort? Have you checked out https://www.php.net/usort?
usort() can accept a comparison function, so you can implement pretty much any ordering rules you want.
排序算法不依赖于比较机制,只依赖于它返回一致的排序。您需要的是一个允许您指定自己的比较函数的排序例程。
Php 提供了三种:usort()、uasort() 和 uksort()。
Sorting algorithms don't depend on the mechanics of the comparison, only that it returns a consistent ordering. What you need is a sorting routine that allows you to specify your own comparison function.
Php provides three: usort(), uasort(), and uksort().