On 09/25/2010 09:05 PM, 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 ☄
Python 3: (I have not tried to match the exact format of your output,
but I get the right things is the right order.)
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'))
from collections import OrderedDict
r = OrderedDict()
for label,*rest in data:
r.setdefault(label, []).extend(rest)
print(list(r.values()))
produces:
(['a', 'b'], ['c', 'd', 'i', 'j'], ['e', 'f', 'k', 'l', 'o', 'p'], ['g',
'h'], ['m', 'n', 'q', 'r'], ['s', 't'])
--
Gary Herron, PhD.
Department of Computer Science
DigiPen Institute of Technology
(425) 895-4418
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