Examples of four basic sorting algorithms in PHP

1. Bubble sort

Idea analysis: In a set of numbers to be sorted, compare and adjust the two adjacent numbers in sequence from front to back for the sequence that has not yet been sorted. , let the larger numbers sink and the smaller numbers rise. That is, whenever two adjacent numbers are compared and it is found that their ordering is opposite to the ordering requirement, they are swapped.
Code implementation:
$arr=array(1,43,54,62,21,66,32,78,36,76,39);
function bubbleSort($arr)
{
$len= count($arr);
//This layer of loop controls the number of rounds that need to bubble
for($i=1;$i<$len;$i++)
{ //This layer of loop is used to control each round of bubbling The number of times a number needs to be compared
for ($k=0;$k<$len-$i;$k++)
{
if($arr[$k]>$arr[$k+1])
{
                    $tmp=$arr[$k+1];
return $ arr;
}


2. Selection sort

Code implementation:

function selectSort($arr) {//Double loop is completed, the outer layer controls the number of rounds, and the inner layer controls the number of comparisons $len =count($arr); for($i=0; $i<$len-1; $i++) {                                                                                                                                                                                                     ​=$i+1; $j<$len; $j++) {
                                                                                                                                                                {， // Comparison, find a smaller one, record the position of the minimum value; and use the known minimum value to compare at the next comparison.
                                                                                                                                                                             If it is found that the position of the minimum value is different from the currently assumed position $i, the positions can be interchanged. ! If ($ p! = $ I) {
$ tMP = $ arr [$ p];
$ arr [$ p] = $ arr [$ i];
$ arr [$ i] = $ tmp;
} }
// Return the final result
Return $ arr;
}


3. Insert sorting


thinking analysis: In a set of sorting Insert the nth number into the previous ordered number so that these n numbers are also in order. Repeat this cycle until everything is in order.

Code implementation:
function insertSort($arr) {
$len=count($arr);
for($i=1, $i<$len; $i++) {
$tmp = $arr [$ i]; 内 // Inner circulation control, compare and insert
for ($ j = $ i-1; $ j & gt; = 0; $ j-) {
if ($ tmp & lt; j]) {
                                                                                                                                                                           ] = $ Tmp;
} else {
// If you encounter an element that does not need to move, because it is already sorted as an array, then the previous one does not need to be compared again.
                                                                                              break; The first element or the last element. Through one scan, the column to be sorted is divided into two parts, one part is smaller than the reference element, and the other part is greater than or equal to the reference element. At this time, the base element is at its correct position after sorting, and then the two divided parts are sorted recursively in the same way.



Code implementation:


function quickSort($arr) {
//First determine whether you need to continue

if($length <= 1) {         return $ arr; }

$base_num = $arr[0];

//Initialize two Array $left_array = array(); // Smaller than the base $right_array = array(); // Greater than the base for ($i=1; $i<$length; $i++) { if($base_num > $right_array[] = $arr[$ i];
                                                                                                                                                                                                                                  . /Merge
return array_merge($left_array, array($base_num), $right_array);
}

Reference:

http://www.evget.com/article/2015/2/11/22149.html


http://www.evget.com/product/2605



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