二分查找法:前提數組爲有序數組
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 $mid;
//中元素比目標大,查找左部
if($arr[$mid] > $target) $high = $mid - 1;
//重元素比目標小,查找右部
if($arr[$mid] < $target) $low = $mid + 1;
}
//查找失敗
return false;
}