PHP simple selection sorting algorithm example, php algorithm example_PHP tutorial

PHP simple selection sorting algorithm example, php algorithm example

Simple selection sorting algorithm: through n-i comparisons between keywords, select the record with the smallest keyword from n-i+1 records, and combine it with the i-th (1<=i<=n) record Exchange

Copy code The code is as follows:

class Sort{
         /**
* Simple selection sorting
           *                                  * @param unknown_type $arr
                     */
           public function selectSort(&$arr) {
               $len=count($arr);
for ($i=0;$i<$len;$i++) {
                  $min=$i;
for ($j=$i+1;$j<=$len-1;$j++) {
If ($arr[$min]>$arr[$j]) {//If a value smaller than $arr[$min] is found, assign the subscript to $min
                            $min=$j;
                 }
                }
If ($min!=$i){//If $min is not equal to $i, it means the minimum value has been found, then exchange
$this->swap($arr[$i],$arr[$min]);
                }
            }
}
         /**
* Swap the two values ​​​​of $a and $b
                     */
          public function swap(&$a,&$b) {
              $temp=$a;
               $a=$b;
               $b=$temp;
}
}
$arr=array(4,6,1,2,9,8,7,3,5);
$test=new Sort();
$test->selectSort($arr);//Simple selection sort
// var_dump($arr);
?>

Features of simple selection sorting: the number of mobile data exchanges is quite small, thus saving corresponding time

Time complexity analysis of simple selection sort:
Regardless of the best or worst case, the number of comparisons is the same. The i-th sorting requires n-i keyword comparisons, which requires n(n-1)/2 comparisons. So the final time complexity is O(n^2)
Although it is O(n^2) like bubble sort, the performance of selection sort is still slightly better than bubble sort.

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