/**

*二分查找算法

*參數(shù)? ? 名稱? ? 數(shù)據(jù)類型? 備注

*@param? $arr? ? array? ? 數(shù)組

*@param? $target? int? ? ? 要查找的值

*/

public function binarySearch($arr,$target){

????????????$left=0;//第一個(gè)值的下標(biāo)

????????????$right=count($arr)-1;//最后一個(gè)下標(biāo)

????????????while($left <= $right){

????????????????$mid=floor(($left+$right)/2);//中間值的下標(biāo)

????????????????if($arr[$mid] == $target)? ?return $mid;

????????????????if($target > $arr[$mid]) $left=$mid+1;

????????????????if($target < $arr[$mid]) $right=$mid-1;

????????????}

}