# PSE Advent Calendar 2021 (Day 12): Christmas Confusion

This puzzle is part of the Puzzling StackExchange Advent Calendar 2021. The accepted answer to this question will be awarded a bounty worth 100 reputation.

< Previous Door Next Door >

## Part 1:

Tragedy has struck during my family's annual Christmas party! When going to check on the gifts I had prepared for each of my guests, I realized that all of the labels had fallen off! Despite my best efforts to remember who was supposed to get what, I can only remember bits and pieces.

Can you help me correctly label the gifts?

#### People:

• Abraham
• Aine Francis-Finkelstein
• Charles
• Frank
• Giovanni
• Julie S

### Items:

• rumpled note saying "not it"
• cod
• "I hope you have a fun xmas"
• paperback novel about the YMCA
• ewer full of soul
• handful of lira

### Facts:

• Frank arrived immediately after the person getting cod.
• The person getting lira arrived after the person getting the Christmas wishes.
• Aine isn't getting the paperback novel
• The person who arrived last is the one getting the rumpled note.
• One person arrived between Frank and Abraham, and they will be the one getting the paperback novel.
• Julie arrived first.
• Giovanni will be getting the ewer of soul.
• Abraham isn't getting the rumpled note.

## Part 2:

Fortunately, it seems like what I was able to remember was enough the make sure everyone got the gift they were meant to. Everyone loved their gifts, and we spent some time catching up before dinner. Aine told us about her 2 kids: Alex, age 15, and Bella, age 6. Giovanni took the opportunity to remind us that the key to a good celebration is family, to which we all agreed. After spending a bit more time chatting we all headed to our seats. However, our family keeps to a strict seating arrangement, which I'd unfortunately forgotten. Once again, I did recall a few facts that should help puzzle it out.

• The rice fanatic sits somewhere between the chemist and Charles.
• The linguist is somewhere to my left.
• The Albanian sits next to the chemist, but not Frank.
• The pizza connoisseur is on one of the ends.
• There were two people between the rotten board gamer and the turophile.
• I sit in the middle.

Can you extract the seating arrangement?
Also, what am I getting for Christmas?

Hint

Frank is a fan of bacon, but Abraham's religious affiliation prevents him from consuming it.

These seem like rather odd gift ideas, and they don't seem to line up with the second half of the puzzle. Maybe the order of their arrival holds some kind of clue?

• Just to clarify (if you wish to): (i) 'One person arrived between Frank and Abraham' - Should we assume an order here, i.e. that Frank arrives before Abraham? (ii) 'The person getting lira arrived after the person getting the Christmas wishes' - Should we interpret this as immediately after or is this deliberately left ambiguous? Thanks!
– Stiv
Dec 13, 2021 at 13:19
• @Stiv Sure, I can clarify: (i) You should not need to assume an order, as it should be logically derivable from the other clues. (ii) This one is deliberately left ambiguous, note how the first clue uses immediately, while this one does not. Dec 13, 2021 at 14:14
• Thanks, and ah yes - I've just seen why my first question is redundant!
– Stiv
Dec 13, 2021 at 14:15
• This claims to offer a 100-point bounty for whoever cracks it, but the other Advent Calendar puzzles only offer 50 points. Is this one just an error? Dec 14, 2021 at 0:47
• @GarethMcCaughan The puzzles on Sundays, like Day 5, are worth extra points. Dec 14, 2021 at 2:44

I'm guessing your Christmas present will be

New socks!

Zizy Archer has solved part 1 giving the order

1. Julie S - cod
2. Frank - "I hope you have a fun xmas"
3. Charles - YMCA
4. Abraham - lira
5. Giovanni - soul
6. Aine FF - not it

are actually ciphered and the names are hints to the cipher. The ciphers are

1. Julie S (Julius Caesar) - Caesar cipher:
This is encrypted using rot-10 (rotten as hinted in part 2), so decrypting cod with rot-16 gives
SET

2. Frank (Francis Bacon) - Bacon's cipher:
We should take the regular letters as 0 and italic letters as 1. Then, decrypting the message gives the word
EDAM

3. Charles (Charles Wheatstone) - Playfair cipher:
Decrypting YMCA using the regular Polybius square
ABCDE
FGHIK
LMNOP
QRSTU
VWXYZ
gives
WOBE

4. Abraham - Atbash cipher:
Decrypting lira gives
ORIZ (Albanian word for rice)

5. Giovanni (Giovan Battista Bellaso) - Vigenère cipher:
This uses the keyword family as hinted in part 2 so decrypting soul gives
NOID

6. Aine FF - Affine cipher:
This uses the transform 15x+6 as the encryption function as hinted in part 2. The decryption can then be done with function 7x+10 so notit gives
XENON

So, now we should have enough information to deduce the arrangement!

Julie S is the board gamer, Frank is the turophile, Charles is the linguist, Abraham is the Albanian rice fanatic, Giovanni is the pizza connoisseur and Aine is the chemist.

Now, since there must be two people between Julie and Frank, they must sit in different sides of the middle, i.e., OP.

Charles is on the left and Aine and Abraham sit next to each other, so they must be on the right and furthermore, they must occupy the last two seats there. Since Abraham cannot be last, the order must be Abraham - Aine.

This leaves the left end for Giovanni and the third place for Charles. Frank cannot be next to Abraham so the final order is
Giovanni - Frank - Charles - OP - Julie - Abraham - Aine

Putting the (decrypted) gifts in the same order gives
Noid - Edam - Wobe - ? - Set - Oriz - Xenon
where the first letters spell out NEW SOX

Partial solution.

Part 1:

There are 8 facts, let's number them 1->8. Names are written with single quotation marks (' '), while presents are in double quotation marks (" "). Now,

Taking facts 1 + 5, we get that order is "cod", 'Frank', "YMCA", 'Abraham'. Now, adding 4 and 8, we get that someone arrived after 'Abraham'. List has 4 items/people already and we need to add 'Giovanni' (7) that is completely outside of this list, so there are 5 and one needs to follow after 'Abraham'/'Giovanni'. From 6, 'Julie' needs to either get "cod" or be before the list - and it obviously cannot be before this list, there are just 6 people.

Therefore,

Julie arrives first and gets "cod". Then Frank arrives. Then someone gets YMCA, then Abraham arrives. Followed by Giovanni that gets "soul". And finally someone else getting "note". From 3, we know this last person is 'Aine'. So, 'Charles' got "YMCA". Only 2 left now, which tells us 'Frank' got "wishes" and 'Abraham' got "lira".

So, the part 1 is solved:

1. 'Julie': "cod"; 2. 'Frank': "wishes"; 3. 'Charles': "YMCA"; 4. 'Abraham': "lira"; 5. 'Giovanni': "soul"; 6. 'Aine': "note".

Now, for part 2. This time, people characterization (eg "rice lover" are in double quotes), 1-6 for clues this time. Things about people, extracted from clues: "rice", "chemist", "linguist", "pizza", "board", "turophile", "Albanian". 'I' is added to the list of 6 people.

Who can be on position 6? "chemist" can be at most on position 5 (clue 1) which would put "Albanian" to position 4 (3) or if "chemist" is on position 4, "Albanian" can be on position 5 as well. "Linguist" is somewhere on the left (2+6), and "pizza" can be only on positions 1 or 7 (4). "board" is at most on position 4 (5). This means we can have "rice" or "turophile" on position 6.

Now, I don't know how to actually solve this on, so some guessing :(

Let's try with "rice" on position 6 first: position 5 can be only "turophile" as we can't put it anywhere else if we start cramming "Albanian" and "chemist" there. This means "board" is on position 2 and "pizza" is on position 7. Position 1 is then "linguist" and positions 3+4 are taken by "chemist" and "Albanian" in any order.