Picat Solutions for the 2025 LPCP Programming Contest Problems

[Neng-Fa Zhou]

Following the tradition, I have completed solutions in Picat for all the five problems used in the 2025  LP/CP Programming Contest. 

https://github.com/nfzhou/lp-contest/blob/main/lp2025_prob1.pi

https://github.com/nfzhou/lp-contest/blob/main/lp2025_prob2.pi

https://github.com/nfzhou/lp-contest/blob/main/lp2025_prob3.pi

https://github.com/nfzhou/lp-contest/blob/main/lp2025_prob4.pi

https://github.com/nfzhou/lp-contest/blob/main/lp2025_prob5.pi

All the solutions, except for Problem 5, use SAT. The solution for Problem 5 employs CP, which is much faster than SAT when repeatedly solving small and easy problems.

I couldn’t get the initial solution for Problem 3 to work on site because it didn’t remove duplicate edges in the hcp(Vs, Es) constraint. Perhaps Picat should issue a warning when Es contains duplicate edges.

The problems this year were significantly more challenging than last year’s. I needed about 10 hours to write the solution for Problem 2. I used ASP Chef to clarify the problem description and verify the solution; without it, completing the solution would have taken much longer."

Thanks to Marco Gavanelli's stellar performance (Marco used ECLiPSe-Prolog),  our p(Picat/Prolog) team won the first place. Congratulations to the team, especially Marco.

Cheers,

Neng-Fa

[David Silverman]

Fantastic!

[Claudio Cesar de Sá]

 Really, another great achievement by PICAT!
by the way, what is the "ASP Chef" as claritier? Is it a site or from LP/CP Programming Contest.

Congrats for you and Marco

cc

[Neng-Fa Zhou]

I should have mentioned a nice feature of Picat used in the solution for Problem-5:

solve_all([$limit(2)],A) = [_]

The limit(N) option limits the number of solutions found by solve_all to N. I remember that Hakan requested the addition of this option. This is really nice to check if there is only a unique solution in a CSP.

Cheers,

NF

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