Bubble Sort

Picture from Wikipedia

 1 <?php
 2 function swap(&$a, &$b){
 3     $c = $a;
 4     $a = $b;
 5     $b = $c;
 6 }
 7 
 8 # bubble sort
 9 # ascend
10 function sortBubble(&$a){ # a is an array of numbers
11 
12     # length of a
13     $m = count($a);
14 
15     if($m < 2){
16         return;
17     }
18 
19     # swap teller
20     $n = 0;
21 
22     # for m numbers, we have m-1 maxes to bubble to the right
23     for($i=1; $i<=$m-1; $i++){
24 
25         # i=1, a max in m numbers to find;               0, m-1
26         # i=2, a max in m-1 numbers on the left to find; 0, m-2 
27         # i=3, a max in m-2 numbers on the left to find; 0, m-3; m-i
28         for($j=0; $j<$m-$i; $j++){
29             if($a[$j] > $a[$j+1]){
30                 swap($a[$j], $a[$j+1]);
31                 $n = 1;
32             }
33         }
34 
35         if($n == 0){ # no swap happened, finish the sort
36             break; # return
37         }
38         else{
39             $n = 0; # reset teller, continue
40         }
41     }
42 
43     return;
44 }
45 
46 $arr = range(5, 0);
47 sortBubble($arr);
48 echo implode(', ', $arr);
49 
50 // 0, 1, 2, 3, 4, 5
51 ?>

 

posted @ 2014-11-09 11:32  crepesofwrath  阅读(338)  评论(0)  编辑  收藏  举报