php二分查找的两种实现方法

递归函数实现：

function  binarySearch($arr, $val, $st, $et){
	$m_ind = $st + floor(($et-$st)/2);
	$max_idx = count($arr)-1;
	$min_idx = 0;
		
	if($arr[$min_idx]>$val || $arr[$max_idx]<$val || ($et-$st==1 && $arr[$et]!=$val && $arr[$st]!=$val)){
			return -1;
	}
		
	if($arr[$m_ind]==$val){
			return $m_ind;
	} else if($arr[$m_ind] > $val){
		$et = $m_ind - 1;
		return binarySearch($arr, $val, $st, $et);
	} else {
		$st = $m_ind + 1;
		return binarySearch($arr, $val, $st, $et);
	}
}

循环实现：

function binarySearch($arr, $val){
	$st = 0;
	$et = count($arr) - 1;
	$m_ind = floor(($et-$st)/2);
	do{
			
		if($arr[$m_ind]==$val){
			return $m_ind;
		} else if($arr[$m_ind] > $val){
			$et = $m_ind - 1;
			$off = ceil(($m_ind-$st)/2);
			if($off == 0) return -1;
			$m_ind = $m_ind - $off;
		} else {
			$st = $m_ind + 1;
			$off = ceil(($et-$m_ind)/2);
			if($off == 0) return -1;
			$m_ind = $m_ind + $off;
		}
	}while(true);
}

　　水平有限，敬请指正！