[英]Sorting an Array of Arrays in PHP --> Need a Good Algorithm
I have an array of 15000 elements each of which is an array of 4 elements. 我有一个15000个元素的数组,每个元素是一个包含4个元素的数组。 I want to sort by the second element of the 4. Originally I made the original array's keys the second element and then k-sorted but unfortunately, some of the second elements are duplicates and since one key can't refer to multiple elements i lost some elements in transition.
我想按照4的第二个元素排序。最初我把原始数组的键作为第二个元素然后k-sorted但不幸的是,一些第二个元素是重复的,因为一个键不能引用我丢失的多个元素转型中的一些要素。 I could bubble sort by the second element but I'm looking for something that runs at least on the order of nlog(n).
我可以通过第二个元素冒泡排序,但我正在寻找至少按nlog(n)顺序运行的东西。 Can anyone think of a good algorithm (or possibly a function in php that I don't know about) that can sort by the second element?
任何人都可以想到一个好的算法(或者可能是我不知道的php中的一个函数)可以按第二个元素排序吗? Thank you!
谢谢!
我认为你可以使用usort
并定义cmp_function来使用第二个元素。
As others have stated, usort or uasort to maintain the array keys is what you want: 正如其他人所说, usort或uasort维护数组键是你想要的:
<?php
$myArray = array(
'fruits' => array(
array('apples', 'oranges', 'bananas')
),
'vegetables' => array(
array('lettuce', 'carrots', 'peas')
),
'monkeys' => array(
array('Curious George', 'Amy', 'Marcel')
)
);
// PHP 5.3+ example using a closure
uasort($myArray, function(array $a, array $b) {
// Use whatever sorting algorithm you like
return strnatcasecmp($a[1], $b[1]);
});
var_export($myArray);
Running the above will output: 运行以上将输出:
array (
'monkeys' =>
array (
0 =>
array (
0 => 'Curious George',
1 => 'Amy',
2 => 'Marcel',
),
),
'vegetables' =>
array (
0 =>
array (
0 => 'lettuce',
1 => 'carrots',
2 => 'peas',
),
),
'fruits' =>
array (
0 =>
array (
0 => 'apples',
1 => 'oranges',
2 => 'bananas',
),
),
)
Here's an example that doesn't use a closure for pre PHP 5.3: 这是一个不在PHP 5.3之前使用闭包的示例:
sortFunc(array $a, array $b)
{
return strnatcasecmp($a[1], $b[1]);
}
uasort($myArray, 'sortFunc');
我不知道usort的内部实现是什么,但我敢打赌它比bubblesort更好(它可能是快速排序)。
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