A wolf, a sheep, and a cabbage need to cross the river...

November 13, 2010 7:51 AM

A Riddle: A wolf, a sheep, and a cabbage need to cross the river. How can you bring them across, one by one, without the sheep eating the cabbage, nor the wolf eating the sheep?

Rubicon, by Gil Alkabetz.

posted by Gator (68 comments total)

In symbolic terms, neither [W]olf & [S]heep, nor [S]heep & [C]abbage can be left alone without the [R]eferee (the solver's avatar) to keep them from killing each other.

0. [WSC] R || []
1. [WC] || [S] R
2. [WC] R || [S]
3. [C] || [WS] R
4. [CS] R || [W]
5. [S] || [WC] R
6. [S] R || [WC]
7. [] || [WSC] R
posted by The Confessor at 8:02 AM on November 13, 2010 [11 favorites]

Where I come from, you would simply juggle them, which means that you would never be 'carrying' more than one at a time.
posted by Dee Xtrovert at 8:05 AM on November 13, 2010 [7 favorites]

Dee Xtrovert: Where I come from, you would simply juggle them, which means that you would never be 'carrying' more than one at a time.

I like your thinking, but how do you row the boat?
posted by Slack-a-gogo at 8:07 AM on November 13, 2010

Shoot the wolf and the sheep?
posted by Avenger at 8:08 AM on November 13, 2010 [2 favorites]

I like the way it's explained in "The Office."
posted by dzaz at 8:09 AM on November 13, 2010 [7 favorites]

You eat them all, then cross the river.
posted by swift at 8:09 AM on November 13, 2010 [3 favorites]

Eat the cabbage and make the wolf swim.
posted by splice at 8:09 AM on November 13, 2010 [1 favorite]

Fancy logic puzzles never accept the reality of powerful animal tranquilizers.
posted by The Whelk at 8:10 AM on November 13, 2010 [36 favorites]

Thanks, Gator. Good fun.
posted by Ahab at 8:10 AM on November 13, 2010

That was teriffic - so inventive! I love the animation, clean and sleak but still really organic. The Escherlike transformation at 3:18-- was really neat.
posted by Wolfdog at 8:13 AM on November 13, 2010

Also: everyone already knows how to solve the riddle. Watch the link.
posted by Wolfdog at 8:14 AM on November 13, 2010 [6 favorites]

5 moves.
posted by kuujjuarapik at 8:15 AM on November 13, 2010

The gag with the out-of-order voices was great, too.
posted by Wolfdog at 8:16 AM on November 13, 2010 [1 favorite]

riverIQGame.swf

The girls can't be left with the man unless the woman is there.
The boys can't be left with the woman unless the man is there.
The burglar can't be left with anyone unless the cop is there.
Only the man, woman, and cop can operate the raft.
posted by rifflesby at 8:17 AM on November 13, 2010 [6 favorites]

That cabbage pisses me off. The other two are all excited about going, bouncing around and everything. Here this guy rented the boat and carries them across the river several times...including an existential trip, a balancing act, moving heaven and earth to get them all there safely...and STILL the cabbage - after all they've been through - just sits there like an ungrateful green turd.
posted by iamkimiam at 8:22 AM on November 13, 2010 [5 favorites]

I like your thinking, but how do you row the boat?

I assmed there was a bridge, not a boat. In my experience, more people cross rivers via bridge than boat. I didn't click on the link though, so my apologies.
posted by Dee Xtrovert at 8:22 AM on November 13, 2010

To be fair, it does bleat, which is more than expressive you usually expect to get out of a cabbage.
posted by Wolfdog at 8:23 AM on November 13, 2010

Don't leave the sheep alone in the boat or there'll be a muttony.
posted by pracowity at 8:27 AM on November 13, 2010 [41 favorites]

I like the way it's explained in "The Office"

Tragically, the link omits the capper: when it comes time to share the solutions, Gareth raises his hand, flips through multiple pages of notes and begins, "Questions..."
posted by ricochet biscuit at 8:28 AM on November 13, 2010

Some nice surprises... well done!
posted by HuronBob at 8:29 AM on November 13, 2010

Yeah, that's how I'd do it.
posted by MrVisible at 8:31 AM on November 13, 2010 [1 favorite]

That cabbage pisses me off. ..just sits there like an ungrateful green turd..

You can get lost in that cabbage. Nothing wrong with cabbage you can lose yourself in.
posted by Ahab at 8:32 AM on November 13, 2010

Stuff the wolf's mouth with the cabbage.
posted by marco_nj at 8:34 AM on November 13, 2010 [3 favorites]

Okay, what's the solution to rifflesby's link? It's driving me nuts!
posted by The Winsome Parker Lewis at 8:44 AM on November 13, 2010

MetaFilter: Propositiones ad Acuendos Juvenes
posted by Smart Dalek at 8:48 AM on November 13, 2010 [1 favorite]

Okay, what's the solution to rifflesby's link? It's driving me nuts!

The key to that one is that, while you can't leave the kids with the grownup of the opposite sex, you can leave the them alone. The implications are fairly disturbing. Also disturbing: when you get them all across, they do some sort of fascist salute/exercise routine. All in all, a very weird puzzle.

But fun.
posted by steambadger at 9:00 AM on November 13, 2010

Personally, if I left a young child alone on the bank of a river, I'd be worried that he or she would either eat poisoned cabbage or be set upon by wolves. But that's just me.
posted by steambadger at 9:01 AM on November 13, 2010

1. Shear sheep.
2. Make yarn out of shorn wool.
3. Affix cabbage to top of sheep's head with yarn so it has a jaunty cabbagehat it can't eat.
posted by Bernt Pancreas at 9:03 AM on November 13, 2010 [20 favorites]

I can't get all four kids together. I can get two boys and one girl, but somebody has to bring the other girl. The man can't bring her, because the woman's not on the other side. The woman can't bring her, because the man's not on the other side. The cop can't bring her, because he'd be leaving the thief with the man and woman. I'm stuck!

Here are the steps I took to get here:

1. Cop and thief
2. Cop
3. Cop and boy
4. Cop and thief
5. Man and boy
6. Man
7. Man and woman
8. Woman
9. Woman and girl
10. Man and woman
posted by The Winsome Parker Lewis at 9:16 AM on November 13, 2010

Hint:

You can leave the thief alone.
posted by Benny Andajetz at 9:24 AM on November 13, 2010

You tie the cabbage to your belt, which is the style at the time.
posted by sciurus at 9:24 AM on November 13, 2010 [12 favorites]

Policeman + criminal + kids on one side is the key...
posted by tksh at 9:41 AM on November 13, 2010

Cannibals and missionaries
posted by Obscure Reference at 9:42 AM on November 13, 2010

A variation of this puzzle made me ragequit Professor Layton. Urgh.
posted by trunk muffins at 9:46 AM on November 13, 2010

Rig the simulation so that the Enterprise can simultaneously defeat all the Romulan warships. Enjoy apple while doing so.
posted by briank at 9:56 AM on November 13, 2010 [12 favorites]

Catapult.
posted by vibrotronica at 10:06 AM on November 13, 2010

Rig the simulation so that the Enterprise can simultaneously defeat all the Romulan warships. Enjoy apple while doing so.

ERR_NOT_ROMULANS
posted by device55 at 10:10 AM on November 13, 2010 [1 favorite]

I did it! Use the cop to start ferrying things once you get to the point where child abuse halts all movement.
posted by EtzHadaat at 10:42 AM on November 13, 2010

jaunty cabbagehat

I'm totally naming my sockpuppet account this.
posted by That's Numberwang! at 10:51 AM on November 13, 2010 [3 favorites]

1. Take sheep across.
2. Score acid from sheep's friend, Curly Earl.
3. QED.

Fantastic find.
posted by chairface at 11:06 AM on November 13, 2010

Bring them each across at different points along the river.
posted by LogicalDash at 11:22 AM on November 13, 2010

Take off and nuke the site from orbit. That's the only way to be sure.
posted by fuq at 12:39 PM on November 13, 2010 [1 favorite]

The cabbage ate the wolf. What am I doing wrong?
posted by NMcCoy at 12:40 PM on November 13, 2010 [5 favorites]

I can dig the sheep and the wolf wanting to cross the river. Why not - they're mobile and it's a free country. But a cabbage? What's it gonna do when it gets to the other side? Put down new roots?? Raise a family?? This is such a prejudiced view of the very limited ambulatory opportunities available to vulnerable members of the brassica tribe. Shame on you.
posted by MajorDundee at 12:57 PM on November 13, 2010

tie a rope to the cabbage. Tie the other end of the rope to the boat. Drop cabbage in water. Put sheep and wolf on boat and row across.

The river is crossed in one step and all the silt has been rinsed out of the cabbage, ensuring non-gritty sauerkraut for dinner!
posted by ardgedee at 1:06 PM on November 13, 2010 [2 favorites]

At some point in the distant past some shepherd came up with the idea that the wolf could through selective breeding be tamed and trained to gaurd the sheep. That person was a genius.
posted by humanfont at 1:35 PM on November 13, 2010 [3 favorites]

Step 1: Throw cabbage across river. If you miss, good riddance.

The sheep may be eager to go, but I think the wolf just has to "go."
posted by galadriel at 1:44 PM on November 13, 2010

This is good. When I teach logic, I give the students bonus puzzles with their assignments, and this riddle is one of the ones I use. I think I'll give a link to this video in the answer key. (It actually serves as the answer, too... the guy is one step away from getting it just before things start going crazy.)
posted by painquale at 1:52 PM on November 13, 2010

I had this question in an interview at Microsoft.

My answer of 'Burying the cabbage and waiting until it's rotton, and then poisoning the wolf with it" was deemed Incorrect. Very creative, but nonetheless incorrect. So then I solved it 'the right way' for them.

They did give me points for the creativity, however.
posted by spinifex23 at 2:04 PM on November 13, 2010

I don't understand how just taking the sheep first is not the answer. Wolves are carnivores, thus the wolf is not going to eat the cabbage.
posted by Sara C. at 2:44 PM on November 13, 2010

And then what next, Sara?
posted by Wolfdog at 2:47 PM on November 13, 2010

(durrrr, I forgot that you also have to deal with the consequences on the other side. Yeah...)
posted by Sara C. at 2:48 PM on November 13, 2010

First take the sheep across, return alone, then take the wolf across, return with sheep, then take sheep and cabbage across. Done.
posted by kenko at 3:00 PM on November 13, 2010

This is just barely related but I want to post it anyway.
posted by joeyjoejoejr at 3:02 PM on November 13, 2010 [1 favorite]

Awesome find! I love this style of animation.
posted by archagon at 4:40 PM on November 13, 2010

Fancy logic puzzles never accept the reality of powerful animal tranquilizers.

Yes, that should work way better than my attempt to tranquilize the cabbage. I don't know what I was thinking.
posted by martinrebas at 5:49 PM on November 13, 2010

The 'family' river game solution goes like this:

1. Cop takes Prisoner. →
2. ← Cop returns.
3. Cop takes Boy1. →
4. ← Cop returns with Prisoner.
5. Dad takes Boy2. →
6. ← Dad returns.
7. Mom and Dad go. →
8. ← Mom returns.
9. Cop takes Prisoner. →
10. ← Dad returns.
11. Mom and Dad go. →
12. ← Mom returns.
13. Mom takes Girl1. →
14. ← Cop returns with Prisoner.
15. Cop takes Girl2. →
16. ← Cop returns.
17. Cop takes Prisoner. →
18. Everyone does weird salute.

And can I just say, that family has some issues.
posted by fontor at 5:59 PM on November 13, 2010 [3 favorites]

Ugh I hate when I sneeze and a cabbage comes out of my nose.
posted by inmediasres at 7:02 PM on November 13, 2010

i must be stupid - all i can think about is that if they're starting on the same side of the river, why haven't they all eaten one another already?
posted by pyramid termite at 7:19 PM on November 13, 2010

Okay, what's the solution to rifflesby's link? It's driving me nuts!

It was driving me nuts, too, so I wrote a program to solve it. Here's a graph of all the reachable states. It's a lot more linear than I would have guessed.
posted by qxntpqbbbqxl at 9:58 PM on November 13, 2010 [1 favorite]

Here's a backstory on the guy you see at the 1:15 mark.
posted by mreleganza at 10:52 PM on November 13, 2010

I'm having a hard time relating this to real life. I need to see it with Tweety, Sylvester, Bulldog, and Granny. Or Ralph and Sam and some sheep. Maybe an anvil.
posted by pracowity at 11:08 PM on November 13, 2010

Fancy logic puzzles never accept the reality of powerful animal tranquilizers.

Listen, I'm having a hard enough time solving this problem as it is. If I start taking animal tranquilizers, I'd have no show.
posted by Infinite Jest at 1:58 AM on November 14, 2010 [5 favorites]

So the animal toilet is on the other side of the river, right?
posted by sour cream at 3:38 AM on November 14, 2010

Ooh! Do Towers of Hanoi next! I love puzzles which can be reduced to cycling between states.
posted by Appropriate Username at 6:44 AM on November 14, 2010

Hey now!

I was just HELPING the sheep into the boat.

AND the wolf.

And, the, ummmmm, cabbage.
posted by Samizdata at 2:22 PM on November 14, 2010

I knew there would be trouble when the hat started moving...
2 Faves: Paddling with wolf, wolf offers paddle...

Thanks Gator!
posted by djrock3k at 2:44 PM on November 14, 2010

Is no one else disturbed that the person is potentially introducing three invasive species to the far side of the river???
posted by DevilsAdvocate at 11:12 AM on November 15, 2010 [1 favorite]