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Posted by ZeldorBlat on 07/03/07 22:37
On Jul 3, 6:27 pm, "David T. Ashley" <d...@e3ft.com> wrote:
> "ZeldorBlat" <zeldorb...@gmail.com> wrote in message
>
> news:1183500186.720943.98580@n2g2000hse.googlegroups.com...
>
>
>
> > On Jul 3, 5:25 pm, "David T. Ashley" <d...@e3ft.com> wrote:
> >> Given an integer input, I'd like to find the index in the array of the
> >> element $array[$i] such that it is equal to or less than the input but
> >> $array[$i+1] is larger.
>
> > If the array keys are sequential you could use array_reduce like this:
>
> > function bracketSearch($arr, $val) {
> > return array_reduce($arr, create_function('$v,$w','return $w > ' .
> > $val . ' ? $v : ++$v;'), -1);
> > }
>
> > Alternatively you could just do it the really easy way:
>
> > function bracketSearch($arr, $val) {
> > foreach($arr as $k => $v)
> > if($v <= $val)
> > return $k;
> > }
>
> I would prefer to avoid both of those methods, because interpreting PHP code
> is likely to be MUCH slower than using a built-in function.
>
> For my application, there is another way to do it; but in the general case
> seems like PHP needs another search function.
>
> Although ... a standard binary search might not perform badly, even in PHP,
> as it should be O(log N).
> --
> David T. Ashley (d...@e3ft.com)http://www.e3ft.com (Consulting Home Page)http://www.dtashley.com (Personal Home Page)http://gpl.e3ft.com (GPL Publications and Projects)
You said there were a few hundred elements in your array. In practice
you won't notice any performance difference between either of those
two methods (or any other, for that matter).
Google for "Premature Optimization" and see what you come up with.
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