PHP二分查找-遞歸與非遞歸的範例程式碼分享

<?php
function binarySearch($arr, $val)
{
	$len = count($arr);
	if(!is_array($arr) || $len <= 0){
		return false;
	}
	
	if($val < $arr[0] || $val > $arr[$len-1]){
		return false;
	}
	
	$start = 0;
	$end = $len - 1;
	while($start <= $end){
		$mid = intval(( $end+$start )/2); //中间值
		if($arr[$mid] == $val){
			return $mid;
		}
		
		if($val < $arr[$mid]){
			$end = $mid - 1;
		}else{
			$start = $mid + 1;
		}
	}
	return false;
}

<?php
// 递归
function binarySearch_r($arr, $low, $high, $key)
{
	$len = count($arr);
	if(!is_array($arr) || $len <= 0){
		return false;
	}
	
	if($key < $arr[0] || $key > $arr[$len-1]){
		return false;
	}
	
	if($low <= $high){
		$mid = intval( ($low+$high)/2 );
		if($arr[$mid] == $key){
			return true;
		}
		
		$func_name = FUNCTION;
		if($key < $arr[$mid]){
			return $func_name($arr, $low, $mid-1, $key);
		}
		else{
			return $func_name($arr, $mid+1, $high, $key);
		}
	}
	return false;
}