To count number of quadruplets with sum = 0
Fri Mar 16 04:08:46 CET 2007
Paul Rubin <http://phr.cx@NOSPAM.invalid> writes:
> print sum([da.get(-(p+q), 0) for p in quads for q in quads])
The above should say:
print sum(da.get(-(p+q), 0) for p in quads for q in quads)
I had to use a listcomp instead of a genexp for testing, since I'm
still using python 2.3, and I forgot to patch that before pasting to
the newsgroup. But the listcomp will burn a lot of memory when the
list is large.
I'd be interested in the running time of the above for your large data set.
Note that it still uses potentially O(n**2) space.
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