php basic search algorithm

1, sequential search

 

 1 function line_search($array,$tar)
 2 {
 3     if(!is_array($array) || count($array) < 1) return false;
 4     for($i=0;$i<count($array);$i++){
 5         if($array[$i] == $tar){
 6             return $i;
 7         }
 8     }
 9     return false;
10 }
11 
12 line_search($arr,34);

2, a binary search

1  // nonrecursive 
2  function binary_search ( $ Array , $ the tar )
 . 3  {
 . 4      IF (! Is_array ( $ Array ) || COUNT ( $ Array ) <1) return  to false ;
 . 5          // array must be sorted 
. 6      Sort ( $ Array );
 . 7      $ High = COUNT ( $ Array ) -. 1 ;
 . 8      $ Low = 0 ;
 . 9      the while ( $ Low <=$high){
10         $middle = intval(($high + $low) / 2);
11         if($array[$middle] > $tar){
12             $high = $middle - 1;
13         }elseif($array[$middle] < $tar){
14             $low = $middle + 1;
15         }else{
16             return $middle; 
17         }
18     }
19     return false;
20 }
21 
22 binary_search($arr,165.4);

 

 1 // 递归
 2 function binary_search($array,$tar,$high=0,$low=0)
 3 {
 4     if(!is_array($array) || count($array) < 1) return false;
 5     sort($array);
 6     if($low <= $high){
 7         $middle = intval(($high + $low) / 2);
 8         if($array[$middle] > $tar){
 9             $high = $middle - 1;
10             echo $high."</br>";
11             return binary_search($array,$tar,$high,$low);
12         }elseif($array[$middle] < $tar){
13             $low = $middle + 1;
14             return binary_search($array,$tar,$high,$low);
15         }else{
16             return $middle; 
17         }
18     }
19     return false;
20 }
21 
22 binary_search($arr,125,count($arr),0);