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?
To begin with, I liked this puzzle and appreciated lowering the level of difficulty.
I will address this issue later after explaining my process of thought.
In Boolean algebra the statement " if XXX then YYY" means : either XXX is false or YYY is true or both.
Take two statements like:
Stat.I : if all Eskimos live in Africa then 7>5,
Stat.iI : if all Eskimos live in Africa then 7<5. Both statements are true and convey the followinmessage: IF the XXX part is false - no need to read the rest.
Now back to our apartments. Let us denote by adbc an arrangement in which the
tenant a lives in the 1st
from the West apt, d in the 2nd etc, no landlord specified, while dbaC means THAT the tenant d lives in the 1st from the West apt, b in the 2nd etc, and the landlord is C.
Reading the 2nd part of the
2-5 statements one grasps immediately that the "results" are mutually exclusive, so there are only 4 IGs (initial guesses)":Axxx, xBxx, xxCx, xxxD (x denotes a regular tenant, not the owner).
Starting with any initial guess, checking it against the conditional statement and modifying it when needed, amd/or backtracking upon contradiction you arrive to the right solution in no time.
I have started with abcd, statements 2 and 3 were in the "no need to read the rest" category; statement 4 implied
a change either to adCb or daCb
and statement 5 left only one valid answer I.e. daCb.
My interpretation of "One of them was a landlord", was and is "Only one of them was a landlord".
Assuming also that ONLY ONE POSSIBLE solution exists, I stopped here.
One might argue that I was lucky with my choice of IG,
-just for fun I've tried two other IGs and in both cases it was a very short process reaching the same conclusion.
Maybe D1 is not a must and D2 SEEMS A REASONABLE COMPROMISE, but in no way a logical puzzle solvable like this one justifies a D3.
To end with a ppositive note: GOOD PUZZLE!
Edited on February 8, 2013, 1:23 pm