PHP associative array sorting (quick sort)_PHP tutorial-PHP Tutorial-php.cn

PHP associative array sorting (quick sort)_PHP tutorial

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Release： 2016-07-13 17:54:25

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Usage environment and conditions
There is a situation where the associative array in PHP has the following array data:
[php]
$array = array (
array (
              'name' => "xiao",
               'age' => 3                                                     ),
array (
               'name' => 'wang',
               'age' => 1                                                   ),
array (
               'name' => 'chen',
               'age' => 2                                     ) )
);

We want to sort the array against the age field. PHP’s built-in function, no matter what kind of sort, obviously cannot meet our needs, so we can write a quick sort code ourselves to quickly achieve our requirements.

Pay attention to the situation

There are no pointers in PHP, so when we want to pass by reference, we can't write quicksort (int *A, int begin, int end) directly like the C code. Instead, we have to use PHP's & operator. Pass the address of the array to the quick sort function, so that you can pass by reference instead of by value in PHP

Quick sort code
[php]

QuickSortProcess ( $array, 0, count ( $array ) - 1 );

print_r ( $array );

/**
* Description: Get the position of the pivot point in quick sort
*/
function QuickPartition(&$array, $left, $right) {
// 1. Baseline definition
$stand = $array [$left];

// 2. Scan from both ends of the interval to the middle until $left == $right
while ( $left < $right ) {
While ( $left < $right && $array [$right] ['age'] >= $stand ['age'] ) {
              $right --;
         }
If ($left < $right) {
$array [$left ++] = $array [$right];
         }
                                                        while ( $left < $right && $array [$left] ['age'] <= $stand ['age'] ) {
$left ++;
         }
If ($left < $right) {
$array [$right --] = $array [$left];
         }
}

// 3. Get the pivot point position
$array [$left] = $stand;
Return $left;
}

/**
* Description: Quick sort main process function
*/
function QuickSortProcess(&$array, $begin, $end) {
// 1. Variable definition
$pivot = NULL; // Pivot point

If ($begin < $end) {
$pivot = QuickPartition ($array, $begin, $end);
QuickSortProcess ( $array, $begin, $pivot - 1 );
QuickSortProcess ( $array, $pivot + 1, $end );
}
}

I used this quick sort in my project, and I was very happy. It was not in vain that I spent N days on the AC quick sort c code during the October 1st holiday