toy list processing problem: collect similar terms

[Nick Mellor]

Oops! Not that sort stability is used in this algorithm. Was thinking of something else :-)

N

On Thursday, 7 February 2013 10:25:36 UTC+11, Nick Mellor  wrote:
> Python 3 version:
> 
> 
> 
> from collections import defaultdict
> 
> 
> 
> data = ((0,'a','b'),(1,'c','d'),(2,'e','f'),(3,'g','h'),(1,'i','j'),(2,'k','l'),(4,'m','n'),(2,'o','p'),(4,'q','r'),(5,'s','t'))
> 
> 
> 
> register = defaultdict(list)
> 
> for number, *letters in data:
> 
>     register[number].extend(letters)
> 
> final = []
> 
> for i in sorted(register.keys()):
> 
>     final.append(register[i])
> 
> print (final)
> 
> 
> 
> NB sorting is "stable" in Python, so sorted() will always keep the 1's, 2's etc in the same order as they were in the unsorted list.
> 
> 
> 
> Nick
> 
> 
> 
> On Sunday, 26 September 2010 14:05:13 UTC+10, Xah Lee  wrote:
> 
> > here's a interesting toy list processing problem.
> 
> > 
> 
> > I have a list of lists, where each sublist is labelled by
> 
> > a number. I need to collect together the contents of all sublists
> 
> > sharing
> 
> > the same label. So if I have the list
> 
> > 
> 
> > ((0 a b) (1 c d) (2 e f) (3 g h) (1 i j) (2 k l) (4 m n) (2 o p) (4 q
> 
> > r) (5 s t))
> 
> > 
> 
> > where the first element of each sublist is the label, I need to
> 
> > produce:
> 
> > 
> 
> > output:
> 
> > ((a b) (c d i j) (e f k l o p) (g h) (m n q r) (s t))
> 
> > 
> 
> > a Mathematica solution is here:
> 
> > http://xahlee.org/UnixResource_dir/writ/notations_mma.html
> 
> > 
> 
> > R5RS Scheme lisp solution:
> 
> > http://xahlee.org/UnixResource_dir/writ/Sourav_Mukherjee_sourav.work_gmail.scm
> 
> > by Sourav Mukherjee
> 
> > 
> 
> > also, a Common Lisp solution can be found here:
> 
> > http://groups.google.com/group/comp.lang.lisp/browse_frm/thread/5d1ded8824bc750b?
> 
> > 
> 
> > anyone care to give a solution in Python, Perl, javascript, or other
> 
> > lang? am guessing the scheme solution can be much improved... perhaps
> 
> > using some lib but that seems to show scheme is pretty weak if the lib
> 
> > is non-standard.
> 
> > 
> 
> >  Xah ∑ xahlee.org ☄