PHP selection sorting method to implement array sorting instance analysis, array instance analysis _php Tutorial

PHP selection sorting method to implement array sorting example analysis, array instance analysis

In this paper, we analyze the method of sorting the array by choosing the method of PHP. Share to everyone for your reference. The specific analysis is as follows:

The basic idea of choosing a sorting method is to illustrate it directly with a case, such as an array $arr = Array (2,6,3,9), from large to small.

First big loop: It first assumes $arr[0] is the maximum value, then compares it with $arr[1]~ $arr [3], and if it is larger, it is exchanged, the process is such (2,6,3,9)---2 and 6 than---> (6,2,3,9)---6 and 3--- > (6,2,3,9)---6 and 9 than---> (9,2,3,6). Note that the subscript here also needs to change.

Second big cycle: assuming $arr[1] Max (excluding $arr[0]), compared with $arr[2]~ $arr [3], the process is such (9,2,3,6)----2 and 3 than----> (9,3,2,6)---3 and 6 than---> ( 9,6,2,3).

The third big cycle: assuming $arr[2] max, compared to $arr[3], the process is like this (9,6,2,3)---2 and 3 than---> (9,6,3,2)

In the same way, after N-1 cycles, you can arrange them.

The PHP code is as follows, and here is the same wrapper with the function

<?phpfunction selectsort (& $arr) {for ($i =0; $i
 
  <$arr[$j]){ $arr[$j]="$arr[$i];" $arr[$i]="$max;" }="" return="" $arr;}$myarr="array(2,6,3,9);selectSort($myarr);echo">
  
  ";p Rint_r ($myarr);? >
 

Code Analysis:

First big cycle:

$i =0 Array (2,6,3,9)
$j = 1, performs 2 and 6 ratios: becomes $arr[0]=6, $arr [1]=2, $max =6 (6,2,3,9)
$j = 2, perform 3 and 6 ratio: do not execute
$j = 3, performs 9 and 6 ratios: becomes $arr[0]=9, $arr [3]=6, $max =9 (9,2,3,6)

Second big cycle:

$i =1, $max = $arr [1]=2, Array (9,2,3,6)
$j = 2, performs 3 and 2 ratios: becomes $arr[1]=3, $arr [2]=2, $max =3 (9,3,2,6)
$j = 3, performs 6 and 3 ratios: becomes $arr[1]=6, $arr [3]=3, $max =6 (9,6,2,3)

The third big cycle:

$i =2, $max = $arr [2]=2, Array (9,6,2,3)
$j = 3, performs 3 and 2 ratios: becomes $max[2]=3, $arr [3]=2, $max =3 (9,6,3,2)

I hope this article is helpful to everyone's PHP programming.

http://www.bkjia.com/PHPjc/959115.html www.bkjia.com true http://www.bkjia.com/PHPjc/959115.html techarticle PHP Selection Sorting method to achieve array Sorting example analysis, array instance analysis in this paper, we analyze the method of selecting sorting by PHP to realize array sorting. Share to everyone for your reference. Specific analysis ...

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