php二分查找

// 递归版本

function bin_sch($arr,$low,$high,$val)
{
　　if($low<$high){
                $mid = intval(($low+$high)/2);
                if($val == $arr[$mid]){
                    return $mid;
                }else if($val < $arr[$mid]){
                     return bin_sch($arr,$low,$mid-1,$val);
                }else{
                    return bin_sch($arr,$mid+1,$high,$val);
                }
        }
        return -1;
}                        

// 非递归版本

 

function bin_sch($arr,$val)
{
     $num = count($arr);
     $low = 0;
     $high = $c - 1;
     while($low <= $high){
          $mid = intval(($low + $high)/2);
          if($val <  $arr[$mid]){
              $mid++;
          }else if($val > $arr[mid]){
              $high--;
          }else{
              return $mid;
         }
     }
     return -1;
}