From: Robert Klemme <bob.news@...>
Date: 2004-07-11T23:27:26+09:00
Subject: Re: A little algorithmic help requested...


"George Ogata" <g_ogata@optushome.com.au> schrieb im Newsbeitrag
news:877jtaltuz.fsf@optushome.com.au...
> Hal Fulton <hal9000@hypermetrics.com> writes:
>
> > Here's a problem my tired brain is having trouble with.
> >
> > Given a sorted array of integers, convert them into as many
> > ranges as possible (ranges of three or more).
> >
> > Example:
> > [1,2,3,4,6,7,8,11,12,15,16,17] ==> [1..4,6..8,11,12,15..17]
>
> Interesting one to golf with:
>
> a.each_index{|i|a[i..j=i+2]==[x=a[i],x+1,x+2]and(0while
a[j]+1==a[j+=1];a[i..j-=1]=a[i]..a[j])}

Great!  I was going to suggest the more conventional

aa = [1,2,3,4,6,7,8,11,12,15,16,17]

a = aa.dup

ranges = []
first = last = a.shift

a.each do |i|
  if i - last == 1
    last = i
  else
    ranges << (first..last)
    first = last = i
  end
end

ranges << (first..last)

p ranges

    robert