标签：style blog http io color ar sp for div
We have 8 numbers. Sort as ascend.
1st loop, we compare 7 times (for 8 numbers), and found the largest 8.
2nd loop, we compare 6 times (for 7 numbers), and found the largest 7.
...
1, 7, 8
2, 6, 7
3, 5, 6
4, 4, 5
5, 3, 4
6, 2, 3
7, 1, 2
In conclusion:
For sorting 8 numbers, we need an outer loop of 7 times, each time for finding a largest number; and an inner loop from comparing 7 times to comparing 1 time (as in the center column).
Implementation in PHP:
1 <?php 2 /* bubble sort: 3 1. operate directly on the input array (&), not on a copy 4 2. sort as ascend 5 6 a is array 7 m is length of a 8 n is times of sort 9 i/j is for-loop counter 10 w is for value swap 11 */ 12 function sortBubble(&$a){ 13 $m = count($a); 14 $n = $m - 1; 15 for($i=0; $i<$n; $i++){ 16 for($j=0; $j<$n-$i; $j++){ 17 if($a[$j] > $a[$j+1]){ 18 $w = $a[$j]; 19 $a[$j] = $a[$j+1]; 20 $a[$j+1] = $w; 21 } 22 else{ 23 // do nothing 24 } 25 } 26 // see the results after each outer loop 27 // echo implode(‘, ‘, $a).‘<br />‘; 28 } 29 } 30 31 $arr = array(9, 5, 2, 7, 3); 32 sortBubble($arr); 33 echo implode(‘, ‘, $arr); 34 35 // 2, 3, 5, 7, 9 37 ?>
标签：style blog http io color ar sp for div
原文地址：http://www.cnblogs.com/crepesofwrath/p/4084714.html
