To count number of quadruplets with sum = 0
Paul Rubin
http
Fri Mar 16 01:59:52 EDT 2007
"n00m" <n00m at narod.ru> writes:
> h = collections.defaultdict(itertools.repeat(0).next)
Something wrong with
h = collections.defaultdict(int)
?????
> for x in e:
> for y in r:
> sch += h[-(x + y)]
That scares me a little: I think it makes a new entry in h, for the
cases where -(x+y) is not already in h. You want:
for x in e:
for y in r:
sch += h.get(-(x+y), 0)
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