From: Joe <qbproger@...>
Date: 2007-12-11T09:06:18+09:00
Subject: Re: [QUIZ] Word Loop (#149)

/(.*?)(.)(.(?:..)+?)\2(.*)/i

break it up:
(.*?) looks for a non-greedy string of anything
(.) any character
(.(?:..)+?) non-greedy matching of an odd number of characters.  I'm
not sure what the ?: adds to the regular expression.
I got this: "(?: )      grouping without backreferences" from here:
http://www.zenspider.com/Languages/Ruby/QuickRef.html#11
\2 matches the any character from before
(.*) a string of any length at the end

i - at the end that means case insensitive.

Joe

On Dec 10, 2007 1:14 PM, Michal Suchanek <hramrach@centrum.cz> wrote:
>
> On 09/12/2007, Ken Bloom <kbloom@gmail.com> wrote:
> >
> > def loopword word
> >   matchinfo=
> >     word.match(/(.*?)(.)(.(?:..)+?)\2(.*)/i)
> >   if matchinfo
> >     _,before,letter,looplets,after=matchinfo.to_a
> >     pad=" "*before.size
> >     after.reverse.split(//).each{|l| puts pad+l}
> >     looplets=looplets.split(//)
> >     puts before+letter+looplets.shift
> >     until looplets.empty?
> >       puts pad+looplets.pop+looplets.shift
> >     end
> >   else
> >     puts "No loop."
> >   end
> > end
> >
> > loopword "Mississippi"
> > puts
> > loopword "Markham"
> > puts
> > loopword "yummy"
> > puts
> > loopword "Dana"
> > puts
> > loopword "Organization"
> >
> >
> > outputs:
> >
> >  i
> >  p
> >  p
> > Mis
> >  ss
> >  si
> >
> > Ma
> > ar
> > hk
> >
> > yu
> > mm
> >
> > No loop.
> >
> > n
> > Or
> > ig
> > ta
> > an
> > zi
> >
> > (The last is a testcase which makes sure that I get the #shifts and #pops
> > right)
> >
>
> I thought this one is too easy once you understand what it is about
> but people always come up with difficult solutions. I wish I knew what
> the regexp does :S
>
> For those who cannot understand it either:
>
> def indexes l, i
>   res = []
>   ptr = 0
>   while (ptr = l.index i, ptr)
>     res << ptr
>     ptr+=1
>   end
>   res
> end
> # .
> #.c1=c5..c2
> # .       .
> # c4.....c3
> def draw_loop word, c1, c5
>   length = (c5 - c1) -4
>   width = length/4
>   height = length/2 - width
>   word = word[0..0].upcase + word[1..-1]
>   c2 = c1 + width +1
>   c3 = c2 + height +1
>   c4 = c3 + width +1
>   word[(c5+1)..-1].reverse.scan(/./).map{|c| " "*c1 + c + "\n"}.join +
>     word[0..c2] + "\n" +
>     (1..height).map{|i| " "*c1 + word[c5 - i].chr + " "*width +
> word[c2 + i].chr + "\n"}.join +
>     " "*c1 + word[c3..c4].reverse + "\n"
> end
> def wloop word
>   word=word.downcase
>   tried=[]
>   ptr=0
>   while ptr < word.length
>     if tried.include? word[ptr]
>       ptr+=1
>       next
>     end
>     char = word[ptr]
>     tried << char
>     pos = indexes word, char
>     next unless pos.length > 1
>     i, j = 0
>     while i < pos.length - 1
>       j=pos.length - 1
>       while j > i
>         diff = pos[j] - pos[i]
>         if (diff)>=4 && (diff) % 2 == 0
>           return draw_loop word, pos[i], pos[j]
>         end
>         j-=1
>       end
>       i+=1
>     end
>     ptr += 1
>   end
>   "No loop \n"
> end
>
>