二分法查找

<?php//二分法查找 前提条件是 数组必须是有序的$arr = array(-3,-1,0,6,9,78,100);//二分法查找function search(&$arr,$findVal,$leftIndex,$rightIndex){if($leftIndex>$rightIndex){echo '找不到！';return ;}$middle = round(($leftIndex+$rightIndex)/2);//中间的下标if($findVal > $arr[$middle]){//查找的数大于中间的数值search(&$arr,$findVal,$middle+1,$rightIndex);}else if($findVal < $arr[$middle]){search(&$arr,$findVal,$leftIndex,$middle-1);}else{echo '找到了，下标是：'.$middle;}}search($arr,7,0,count($arr)-1);?>