Summary of various methods of php array sorting_PHP tutorial

In PHP, it is very simple for us to sort one-dimensional arrays. We only need to use sort(), rsort() and it is done. If we want to sort multi-dimensional data, PHP does not have such a function, so we need it. Did it myself.

For php array sorting PHP provides a lot of functions. I will list them below. If not, you can add them.

The sort() function is used to sort array cells from low to high.
The rsort() function is used to sort array cells from high to low.
The asort() function is used to sort the array cells from low to high and maintain the index relationship.
The arsort() function is used to sort the array cells from high to low and maintain the index relationship.
The ksort() function is used to sort array cells from low to high by key name.
The krsort() function is used to sort array cells from high to low by key name.

But today we are mainly talking about the array sorting function that comes with PHP, mainly about custom sorting

1. Bubble sorting method
Description: Find the largest number, arrange it to the end, and then continue to find

Example:

The code is as follows

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$arr = array(3,5,- 1,0,2);

代码如下	复制代码
$arr = array(3,5,-1,0,2); for($i=0;$i for($j=0;$j if($arr[$j]>$arr[$j+1]){             $temp = $arr[$j];             $arr[$j]=$arr[$j+1];             $arr[$j+1]=$temp;         }     } }

for($i=0;$i for($j=0;$j If($arr[$j]>$arr[$j+1]){
               $temp = $arr[$j];
               $arr[$j]=$arr[$j+1];
               $arr[$j+1]=$temp;
}
}
}

Understanding:
3, 5, -1, 0, 2
//Start from the first number and compare backwards. If it is larger than the following number, adjust the position with the following number
//The first time, 3 is less than 5, then it remains unchanged
//The second time, 5 is greater than -1, then it becomes
3, -1, 5, 0, 2
//The third time, 5 is greater than 0
3, -1, 0, 5, 2
//The fourth time, 5 is greater than 2
3, -1, 0, 2, 5
This completes an inner loop. At this time, the last number is sorted and will not participate next time 3, -1, 0, 2, 5 The second outer loop begins. The first time: 3 is greater than -1

代码如下	复制代码
$arr=array(2,1,-1,3,0); for($i=0;$i $minval = $arr[$i]; $minindex = $i; for($j=1+$i;$j if($arr[$j]<$minval){ $minval = $arr[$j]; $minindex = $j; } } $temp = $arr[$i]; $arr[$i] = $arr[$minindex]; $arr[$minindex] = $temp; }

-1, 3, 0, 2, 5<🎜> The second time: 3 is greater than 0<🎜> -1, 0, 3, 2, 5<🎜> The third time: 3 is greater than 2<🎜> -1, 0, 2, 3, 5<🎜> This completes the sorting of the next two digits, and so on<🎜> -1, 0, 2, 3, 5 <🎜> 2. Selection sorting method Description: First assume that the first number is the smallest number, and then compare the following numbers with it in turn. If the assumed number is not the smallest number, swap its position with the following smallest number <🎜 >

The code is as follows	Copy code
$arr=array(2,1,- 1,3,0);<🎜> for($i=0;$i $minval = $arr[$i];<🎜> $minindex = $i;<🎜> for($j=1+$i;$j If($arr[$j]<$minval){<🎜>                $minval = $arr[$j];<🎜>                $minindex = $j;<🎜> }<🎜> }<🎜> $temp = $arr[$i];<🎜> $arr[$i] = $arr[$minindex];<🎜> $arr[$minindex] = $temp;<🎜> }<🎜>

Understanding:
2, 1, -1, 3, 0
//Assume that the first number 2 is the minimum value, and the subsequent numbers are compared with 2 in turn to find the smallest number
Process:
1 is less than 2, then minval=1
-1 is less than 1, then minval=-1
3 is greater than -1, unchanged
0 is greater than -1, unchanged
So now we have found the smallest number in the array, which is -1
Swap the positions of -1 and 2 to complete the sorting of the first number
So now the array becomes
-1, 1, 2, 3, 0
Now the first number -1 is already in order, so it will not participate in the comparison and continue to the next
Now assume minval=1
2 is greater than 1, unchanged
3 is greater than 1, unchanged
0 is less than 1, then minval=0
Now that one cycle is completed, swap the positions of 0 and 1 to complete the sorting of the second number
So now the array becomes
-1, 0, 2, 3, 1
//The following push method is the same as above. . .

3. Insertion sort method description: First assume that the first number in an array is a separate ordered array, and then compare the following number with it [as I grows here, it becomes them]. If If the following number is smaller than the assumed number, move the smaller number back, and finally move that number to the front

The code is as follows

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$arr=array(2,1,- 1,3,0);

代码如下	复制代码
$arr=array(2,1,-1,3,0); for($i=1;$i $insertval=$arr[$i]; $insertindex = $i-1; while($insertindex>=0 && $insertval<$arr[$insertindex]){ $arr[$insertindex+1]=$arr[$insertindex]; $insertindex--; } $temp = $arr[$i]; $arr[$insertindex+1]=$insertval; }

for($i=1;$i $insertval=$arr[$i];<🎜> $insertindex = $i-1;<🎜> While($insertindex>=0 && $insertval<$arr[$insertindex]){<🎜>           $arr[$insertindex+1]=$arr[$insertindex];<🎜>          $insertindex--;<🎜> }<🎜> $temp = $arr[$i];<🎜> $arr[$insertindex+1]=$insertval;<🎜> }<🎜>

Understanding:
2, 1, -1, 3, 0
//For the first time, save the number 1 to be inserted as insertval, and then compare insertval with 2. 1 is less than 2, so move 2 back to become the following picture
2, 2, -1, 3, 0
//At this time, there is no number in front of 2, insertindex=0, so the comparison is completed, then insert insertval to the found position. It becomes as shown below
1, 2, -1, 3, 0
//At this time, 1 and 2 become ordered arrays
//The second time, first save the number to be inserted -1 as insertval, and then compare insertval with 2. -1 is less than 2, so move 2 back to become the following picture
1, 2, 2, 3, 0
//At this time, compare insertval with 1. If -1 is less than 1, then move -1 back to become the following picture (this is a process of comparing the number to be inserted with the previous ordered array)
1, 1, 2, 3, 0
//At this point, insertindex has come to an end, so insert insertval at this position
-1, 1, 2, 3, 0
//The following method is as above

The two-dimensional array sorting function can achieve an ORDER BY effect similar to MySQL. It has special applications when the array is not obtained from the database.

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The code is as follows

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// Description: Sorting method of two-dimensional array in PHP   /**  * @package     BugFree  * @version     $Id: FunctionsMain.inc.php,v 1.32 2005/09/24 11:38:37 wwccss Exp $  *  *  * Sort an two-dimension array by some level two items use array_multisort() function.  *  * sysSortArray($Array,"Key1","SORT_ASC","SORT_RETULAR","Key2"……)  * @author                      Chunsheng Wang  * @param  array   $ArrayData   the array to sort.  * @param  string  $KeyName1    the first item to sort by.  * @param  string  $SortOrder1  the order to sort by("SORT_ASC"|"SORT_DESC")  * @param  string  $SortType1   the sort type("SORT_REGULAR"|"SORT_NUMERIC"|"SORT_STRING")  * @return array                sorted array.  */ function sysSortArray($ArrayData,$KeyName1,$SortOrder1 = "SORT_ASC",$SortType1 = "SORT_REGULAR") {     if(!is_array($ArrayData))     {         return $ArrayData;     }       // Get args number.     $ArgCount = func_num_args();       // Get keys to sort by and put them to SortRule array.     for($I = 1;$I < $ArgCount;$I ++)     {         $Arg = func_get_arg($I);         if(!eregi("SORT",$Arg))         {             $KeyNameList[] = $Arg;             $SortRule[]    = '$'.$Arg;         }         else         {             $SortRule[]    = $Arg;         }     }       // Get the values according to the keys and put them to array.     foreach($ArrayData AS $Key => $Info)     {         foreach($KeyNameList AS $KeyName)         {             ${$KeyName}[$Key] = $Info[$KeyName];         }     }       // Create the eval string and eval it.     $EvalString = 'array_multisort('.join(",",$SortRule).',$ArrayData);';     eval ($EvalString);     return $ArrayData; }   //################# 示例 ################# $arr = array(     array(         'name'      =>   '学习',         'size'      =>   '1235',         'type'      =>   'jpe',         'time'      =>   '1921-11-13',         'class'     =>   'dd',     ),     array(         'name'      =>   '中国功夫',         'size'      =>   '153',         'type'      =>   'jpe',         'time'      =>   '2005-11-13',         'class'     =>   'jj',     ),     array( 'name' =>                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             ), array( 'name' => 'Chinese Kung Fu',                                                                                                                                                                                                                                                                                                                                                                                   'time' => '1925-02-13', 'class' => 'yy', ), array( 'name' => 'Chinese Kung Fu',                                                                                                                                                                                                                                                                                                                                                                                           'time' => '1967-12-13',                                                                                                                                                                                                   ), ); print_r($arr); //Note: 153 is smaller than 65 when sorted numerically $temp = sysSortArray($arr,"name","SORT_ASC","type","SORT_DESC","size","SORT_ASC","SORT_STRING"); print_r($temp); ?> As for one-dimensional array sorting, we can completely implement data sorting using the functions that come with PHP, so what we are talking about are methods that cannot meet our needs using custom functions.

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In php, it is very simple for us to sort one-dimensional arrays. We only need to use sort(), rsort( ) That’s it. If you want to sort multi-dimensional data, PHP doesn’t have this kind of function, so I need this...