Avery , Blake , Clark and Doyle each live in an apartment. Their apartment are arranged like this :
+---+---+---+---+
| A | B | C | D | --> East
+---+---+---+---+
- One of the four is the landlord.
- If Clark's apartment is not next to Blake's apartment, then the landlord is Avery & lives in apartment A.
- If Avery's apartment is east of Clark's apartment, then the landlord is Doyle and lives in apartment D.
- If Blake's apartment is not next to Doyle's apartment, then the landlord is Clark and lives in apartment C.
- If Doyle's apartment is east of Avery's apartment, then the landlord is Blake and lives in apartment B.
Who is the landlord?
I agree with Ady. The only solution is DACB. I solved this by forming the contrapositives of statements 2 - 5, figuring that 3 or 4 of the following predicates need to be true
2. C is next to B
3. A is west of C
4. B is next to D
5. D is west of A
and then logicking out that 4 was false.
But it is almost easier just to list the 24 possible combinations
ABCD -- This makes both B & C the landlord, which contradicts 1
ABDC -- This makes both A & B the landlord, which contradicts 1
ACBD -- contradicts 5
ACDB -- contradicts 5
ADBC -- contradicts 5
ADCB -- contradicts 4
BACD -- contradicts 2
BADC -- contradicts 2
BCAD -- contradicts 4
BCDA -- contradicts 3
BDAC -- contradicts 2
BDCA -- contradicts 2
CABD -- contradicts 2
CADB -- contradicts 2
CBAD -- contradicts 4
CBDA -- contradicts 3
CDAB -- contradicts 2
CDBA -- contradicts 2
DABC -- contradicts 4
DACB -- solution
DBAC -- contradicts 2
DBCA -- contradicts 3
DCAB -- contradicts 2
DCBA -- contradicts 3
Good puzzle. Not a D1.
Two approaches (spoiler)
