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
