二分查找

注：二分查询必须是有序数组

简单的PHP栗子

function Binary($arr,$end){

$low = 0;

$length = count($arr)-1;

while($low <= $length){

$mind = floor(($low+$length)/2);

if($arr[$mind]==$end) return  $mind;

if($arr[$mind]>$end) $lenth = $mind-1;

if($arr[$mind]<$end) $low = $mind+1;

}

return false;

}

$arr = ['1','2','3','5','9'];

print_r(Binary($arr,5));