From: 7stud -- <bbxx789_05ss@...>
Date: 2007-10-30T14:37:14+09:00
Subject: Re: find the closest items in an array to a given value.

Pe単a, Botp wrote:
> have you tried #partition?
> 
> ~> a
> => [1.25, 1, 3, 1.9, 1.95, 2.1, 2.2, 1.5]
> ~> [(parts=a.partition{|i| i<=1.85}).first.max,parts.last.min]
> => [1.5, 1.9]
> 

No, I haven't.  Thanks for pointing the partition method out to me.

I must have been testing my first method on a different, longer array 
because now it runs slightly faster than my second method, as well as 
the partition solution, which makes more sense to me.  Here are the 
results I get:

test1 exec time(1,000,000 loops): 10.348911 total
test2 exec time(1,000,000 loops): 13.916226 total
test4 exec time(1,000,000 loops): 12.912649 total

where test4 is this code:

a = [ 1.25, 1, 3, 2, 3.5, 4.25, 0.65, 1.5, 7.7, 9.2]
target = 1.85

arr = a.partition do |elmt|
  elmt < target
end

closest_lower = arr[0].max
closest_higher = arr[1].min
end

But they are all pretty much equivalent.  inject() is so slow, I just 
hit ctrl-c after what seems like 5 minutes.

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