To count number of quadruplets with sum = 0

[bearophileHUGS at lycos.com]

n00m:
> i have no NumPy to test it...
> without Psyco Anton's code is the winner: ~48sec vs ~58sec of my code
> But with Psyco my runtime is ~28sec; Anton's - ~30sec (PC: 1.6 ghz,
> 512 mb)
> Not so bad.. keeping in mind that 256000 billions quadruplets to
> check :)

I have oiled it a bit, you can try the speed of this too (for dicts in
is always faster than has_key).

from collections import defaultdict
import time, psyco

def main():
    sch = 0
    q,w,e,r = [],[],[],[]
    h = defaultdict(int)

    datafile = file("m1000.txt")
    datafile.next()
    xrows = (map(int, line.split()) for line in datafile)
    q, w, e, r = zip(*xrows)

    for x in q:
        for y in w:
            h[x+y] += 1

    for x in e:
        for y in r:
            if -x-y in h:
                sch += h[-x-y]

    print sch

t = time.clock()
psyco.full()
main()
print round(time.clock() - t, 2), "secs"