Solve Einstein's riddle

Prolog - 954 Characters

m(A,Z):-member(A,Z).
e:-e(Z),w(Z).
e(Z):-Z=[[1,A,F,K,P,U],[2,B,G,L,Q,V],[3,C,H,M,R,W],[4,D,I,N,S,X],[5,E,J,O,T,Y]],m([_,b,r,_,_,_],Z),m([_,s,_,d,_,_],Z),m([_,d,_,_,t,_],Z),m([WH,_,w,_,_,_],Z),m([GH,_,g,_,_,_],Z),GH=:=WH-1,m([_,_,g,_,c,_],Z),m([_,_,_,b,_,p],Z),m([_,_,y,_,_,d],Z),m([3,_,_,_,m,_],Z),m([1,n,_,_,_,_],Z),m([BH,_,_,_,_,b],Z),m([CH,_,_,c,_,_],Z),(BH=:=CH+1;BH=:=CH-1),m([DH,_,_,_,_,d],Z),m([HH,_,_,h,_,_],Z),(HH=:=DH+1;HH=:=DH-1),m([_,_,_,_,b,l],Z),m([_,g,_,_,_,r],Z),m([NH,n,_,_,_,_],Z),m([YH,_,b,_,_,_],Z),(NH=:=YH+1;NH=:=YH-1),m([SH,_,_,_,_,b],Z),m([XH,_,_,_,w,_],Z),(SH=:=XH+1;SH=:=XH-1),p([n,d,b,g,s],[A,B,C,D,E]),p([y,b,r,g,w],[F,G,H,I,J]),p([c,h,b,f,d],[K,L,M,N,O]),p([w,t,m,c,b],[P,Q,R,S,T]),p([d,b,p,r,l],[U,V,W,X,Y]).
t(X,[X|R],R).
t(X,[F|R],[F|S]):-t(X,R,S).
p([W|X],Y):-p(X,V),t(W,Y,V).
p([],[]).
b:-write('+--+--+--+--+--+--+'),nl.
z(A):-writef('|%2L|%2L|%2L|%2L|%2L|%2L|',A),nl.
w([A,B,C,D,E]):-b,z(A),z(B),z(C),z(D),z(E),b.

Output

+--+--+--+--+--+--+
|1 |n |y |c |w |d |
|2 |d |b |h |t |b |
|3 |b |r |b |m |p |
|4 |g |g |f |c |r |
|5 |s |w |d |b |l |
+--+--+--+--+--+--+

Key:

  • First column is house number;
  • Second column is nationality;
  • Third column is favorite color;
  • Fourth column is pet;
  • Fifth column is drink; and
  • Sixth column is cigarette (r = prince, l = bluemaster).

Ruby 322 + input 442

Brute force search of nearly 25 billion possible answers.
My computer would take about 75 days to run this program.
I never verified if this program prints a correct answer!

Run as ruby riddle.rb < riddle.in

riddle.rb (332 bytes)

g=readlines
v=g.shift(5).map &:split
c,*d=v.map{|a|[*a.permutation]}
c.product(*d){|a|(f=eval a.map{|b|b.each_with_index.map{|s,i|"#{s}=#{i}\n"}.join}.join+'g.map{|h|eval h}.all?&&fish')&&(r=['-----------']*5
puts [r,[*0..4],*a,r].map{|s|s.map{|t|'|%11s|'%t}.join},"The #{a[0][f]} in the #{a[1][f]} house owns the fish!")}

riddle.in (442 bytes)

brit dane german norwegian swede
blue green red white yellow
beer coffee milk tea water
blends bluemasters dunhill pall_mall prince
birds cats dogs fish horse
brit==red
swede==dogs
dane==tea
green==white-1
green==coffee
pall_mall==birds
yellow==dunhill
2==milk
norwegian==0
blends==cats-1||blends==cats+1
horse==dunhill-1||horse==dunhill+1
bluemasters==beer
german==prince
norwegian==blue-1||norwegian==blue+1
blends==water-1||blends==water+1

The input file must contain 5 lines of names, followed by lines of logical expressions. House numbers are 0 to 4. There must be a fish.

The program calls Array#permutation five times to find all ways to order the arrays of nationalities, colors, drinks, smokes and pets. The long loop is c.product(*d){|a|...}, calling Array#product to iterate nearly 25 billion possible answers. The loop body has the form (f=eval ...)&&(...). The eval ... part evaluates the logical expressions. If all are true, then f is the house number of the fish and the &&(...) part prints the answer. House number 0 is true in Ruby.

Code golf means not adding code for speed! But I lack 75 days to run the program!


Prolog, 653 characters

a([],L,L).
a([H|T],L2,[H|L3]):-a(T,L2,L3).
m(X,L):-a(_,[X|_],L).
r(X,Y,L):-a(_,[X,Y|_],L).
n(X,Y,L):-r(X,Y,L);r(Y,X,L).
s:-s(S),w(S).
s(S):-length(S,5),m([b,r,_,_,_],S),m([s,_,_,_,d],S),m([d,_,t,_,_],S),r([_,g,_,_,_],[_,w,_,_,_],S),m([_,g,c,_,_],S),m([_,_,_,p,b],S),m([_,y,_,d,_],S),S=[_,_,[_,_,m,_,_],_,_],S=[[n,_,_,_,_],_,_,_,_],n([_,_,_,b,_],[_,_,_,_,c],S),n([_,_,_,d,_],[_,_,_,_,h],S),m([_,_,b,l,_],S),m([g,_,_,r,_],S),n([n,_,_,_,_],[_,b,_,_,_],S),n([_,_,_,b,_],[_,_,w,_,_],S),m([_,_,_,_,f],S).
b:-write('----------------+'),nl.
z(Y,A):-write(Y),writef('|%2L|%2L|%2L|%2L|%2L|',A),nl.
w([S1,S2,S3,S4,S5]):-b,z(1,S1),z(2,S2),z(3,S3),z(4,S4),z(5,S5),b.

Tags:

Code Golf

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