From: Xavier Noria <fxn@...>
Date: 2007-08-03T12:22:45+09:00
Subject: Re: Determining the common prefix for several strings

El Aug 3, 2007, a las 4:46 AM, Xavier Noria escribi�:

>   splits = items.map {|i| i.split(//)}
>   (0...splits.length).each do |i|
>     if splits.map {|s| s[i]}.uniq.length != 1
>       puts items.first[0, i]
>       break
>     end
>   end

There's a bug in the upper limit of the range, it should be the  
length of some element of the splits

   splits = items.map {|i| i.split(//)}
   (0...splits.first.length).each do |i|
     if splits.map {|s| s[i]}.uniq.length != 1
       puts items.first[0, i]
       break
     end
   end

We could compute the length of the shortest string and use that finer  
upper limit, but that's not necessary because even in the case that  
the shortest string is the common prefix, we would get some nil in  
the map through columns in the next iteration, and thus at least two  
distinct values. On the other hand there's the corner case when all  
strings are equal, that's not handled in the above code because they  
way to do it depends on the details.

Please forgive those many revisions, I guess I need some sleep at  
5:22 AM.

-- fxn