PHP二分查找

<?php
#二分查找
function binarySearch(Array $arr, $target) {
$low = 0;
$high = count($arr) - 1;
while($low <= $high) {
$mid = floor(($low + $high) / 2);
#找到元素
if($arr[$mid] == $target) return $mid;
#中元素比目标大,查找左部
if($arr[$mid] > $target) $high = $mid - 1;
#重元素比目标小,查找右部
if($arr[$mid] < $target) $low = $mid + 1;
}
#查找失败
return false;
}

$arr = array(1, 3, 5, 7, 9, 11);
$inx = binarySearch($arr, 1);
var_dump($inx);
?>

float(0)

function binarySearch(Array $arr, $target) {
$mid = ceil(count($arr) / 2);   //取中间位的下标
if ($arr[$mid] < $target) {
$arr = array_slice($arr,$mid);
return binarySearch($arr, $target);
} else if ($arr[$mid] > $target){
$arr = array_slice($arr,0,$mid);
return binarySearch($arr, $target);
} else if{
return $mid;
} else {
return false;
}
}