二分查找 

 1 <?php
 2 
 3 //通过
 4 function bin_search($a_data, $key)
 5 {
 6     $len = count($a_data);
 7     $low = 0;
 8     $high = $len - 1;
 9     while ($low <= $high) {
10         $mid = intval(($high + $low) / 2);
11         if ($key < $a_data[$mid]) {
12             $high = $mid - 1;
13         } elseif ($key > $a_data[$mid]) {
14             $low = $mid + 1;
15         } else {
16             return true;
17         }
18     }
19 
20     return false;
21 }
22 
23 //通过
24 //递归版本
25 function bin_search_recurse($a_data, $low, $high, $key)
26 {
27     if ($low <= $high) {
28         $mid = intval(($low + $high) / 2);
29         if($a_data[$mid] == $key) {
30             return true;
31         } elseif ($key < $a_data[$mid]) {
32             return bin_search_recurse($a_data, $low, $mid - 1, $key);
33         } else {
34             return bin_search_recurse($a_data, $mid + 1, $high, $key);
35         }
36     }
37 
38     return false;
39 }
40 
41 $a_data = [1,2,3,4,5,6,7,8,9];
42 var_dump(bin_search_recurse($a_data, 0, count($a_data) - 1, 30));
43

 

posted @ 2015-11-24 13:59  joy696163  阅读(269)  评论(0)    收藏  举报