From: 7stud -- <bbxx789_05ss@...>
Date: 2009-08-10T08:17:42+09:00
Subject: Re: How to define doubles: Array-to-hash

Bertram Scharpf wrote:
> Here are two:
> 
>   original.inject({}) { |h,e| h[e] ||= 0 ; h[e] += 1 ; h }
> 
> and
> 
>   h = Hash.new { |h,k| h[k] = 0 }
>   original.each { |e| h[e] += 1 }
>   h
> 
> then
> 
>   h.reject! { |k,v| k == 1 }
> 
> Bertram

Your code doesn't produce the desired result, the op wanted an efficient 
solution, and this:

h = Hash.new { |h,k| h[k] = 0 }

is equivalent to:

h = Hash.new(0)


How about a regex?

original = [1, 2, 3, 3, 3, 3, 4, 4, 5]
results = {}

str = original.to_s

str.scan(/((\d)\2+)/).each do |match|
  results[match[1]] = match[0].length
end

p results

--output:--
{"3"=>4, "4"=>2}

...but that is no faster than:


results = Hash.new(0)

original.each do |elmt|
  results[elmt.to_s] += 1
end

results.delete_if {|key, val| val == 1}

p results

--output:--
{"3"=>4, "4"=>2}
-- 
Posted via http://www.ruby-forum.com/.