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angelv
Jul '10

Hi

I've been submitting solutions to the COINS problem (spoj.pl/problems/COINS/) today. I've got accepted the Fortran and the Perl solutions, but I'm having "Wrong answer" in the Haskell solution. I thought that perhaps my code was faulty at some point, but the results for 200K numbers (100K in the upper limit and 100K in the lower one) are exactly as per the Perl solution as can be seen below:

angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$ seq 1000000000 -1 999900001 > p346.in
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$ seq 0 100000 >> p346.in
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$ ./p346.pl < p346.in > p346.po
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$ ghc --make -o p346.exe p346.hs
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$ ./p346.exe < p346.in > p346.ho
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$ diff p346.ho p346.po
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$ head -n 5 p346.ho
4243218150
4243218150
4243218150
4243218150
4243218150
angelv@vaso:~/Dropbox/ProgrammingGym/SPOJ$

Is there any way to find what could be going on?

Cheers,
Ángel de Vicente

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    Jul '10

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stevec
Jul '10

Hi Ángel,

Yes, there is a general technique you can use to investigate unexpected SPOJ server behaviour.
Write tests and use different result status to signal the results.
For example, submit code which simulates an input of 1 000 000 000 and calculates the result.
If the result is the expected number
exit the program - and get "wrong answer"
else
generate a runtime error.

If the test gives a runtime error you have isolated the problem and located the problem input.

Steve