php实现二分查找

<?php
class BinSch{
	/*
	 * 二分查找，针对顺序表才有用
	 */
	public function search($arr,$k,$low,$high){
		if($low<=$high){
			$mid = floor(($low+$high)/2);
		}
		if ($arr[$mid] == $k){
			return $mid;
		}
		
		if($arr[$mid]>$k){
			return $this->search($arr, $k, $low, $mid-1);
		}
		
		if ($arr[$mid]<$k){
			return $this->search($arr, $k, $mid+1, $high);
		}
		
		return false;
	}
}

class Client{
	public static function main(){
		$arr = array(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16);
		$obj = new BinSch();
		echo $obj->search($arr, 10, 0, 15);
	}
}

Client::main();
?>

　　下面是非递归的二分查找

<?php
function serech($arr,$k){
	sort($arr);
	$low = 0;
	$high = count($arr)-1;
	while($low<=$high){
		$mid = ($low+$high)/2;
		if($arr[$mid]<$k){
			$low = $mid+1;
		}elseif ($arr[$mid]>$k){
			$high = $mid-1;
		}else {
			return $arr[$mid];
		}
	}
	return -1;
}
$arr = array(1,2,3,4,6,7,8,9);
$a = serech($arr,5);
var_dump($a);