php基础查找算法

1、顺序查找

 function line_search($array,$tar)
 {
     if(!is_array($array) || count($array) < 1) return false;
     for($i=0;$i<count($array);$i++){
         if($array[$i] == $tar){
             return $i;
         }
     }
     return false;
 }

 line_search($arr,34);

2、二分法查找

 // 非递归
 function binary_search($array,$tar)
 {
     if(!is_array($array) || count($array) < 1) return false;
         // 数组必须排序
     sort($array);
     $high = count($array) - 1;
     $low = 0;
     while($low <= $high){
         $middle = intval(($high + $low) / 2);
         if($array[$middle] > $tar){
             $high = $middle - 1;
         }elseif($array[$middle] < $tar){
             $low = $middle + 1;
         }else{
             return $middle;
         }
     }
     return false;
 }

 binary_search($arr,165.4);

 // 递归
 function binary_search($array,$tar,$high=0,$low=0)
 {
     if(!is_array($array) || count($array) < 1) return false;
     sort($array);
     if($low <= $high){
         $middle = intval(($high + $low) / 2);
         if($array[$middle] > $tar){
             $high = $middle - 1;
             echo $high."</br>";
             return binary_search($array,$tar,$high,$low);
         }elseif($array[$middle] < $tar){
             $low = $middle + 1;
             return binary_search($array,$tar,$high,$low);
         }else{
             return $middle;
         }
     }
     return false;
 }

 binary_search($arr,125,count($arr),0);