prolog code for facebook logic puzzle.

crack_the_code.pl

digit(X) :- member(X,[0,1,2,3,4,5,6,7,8,9]).

code([X,Y,Z]) :- digit(X), digit(Y), digit(Z),
                 rule1([X,Y,Z]),
                 rule2([X,Y,Z]),
                 rule3([X,Y,Z]),
                 rule4([X,Y,Z]),
                 rule5([X,Y,Z]).

rule1([X,Y,Z]) :- X=6 ; Y=8 ; Z=2.

rule2([X,Y,Z]) :- Y=6 ; Z=6 ; X=1 ; Z=1 ; X=4 ; Y=4.

rule3([X,Y,Z]) :- (Y=2, (X=0 ; Z=0)) ; (Z=2, X=0);
                  (Z=2, (X=6 ; Y=6)) ; (Y=2, X=6);
                  (Z=0, (X=6 ; Y=6)) ; (X=0, Y=6).

rule4(C) :- \+ (member(7,C) ; member(8,C) ; member(3,C)).

rule5([X,Y,Z]) :- Y=7 ; Z=7 ; X=8 ; Z=8 ; X=0 ; Y=0.

load into favorite prolog engine, query "?- code(C)." It should produce "C = [0,4,2]; C= [0,6,2]."