Brain Teaser

[Shade]

I heard this brain teaser a few months ago and it flittered through my mind earlier while I was trying to avoid doing more productive things, it's a pretty good one. Figured i'd post it here.

A group of people need to cross a river, they have a raft that can carry two people at a time. The group is made up of a father, a mother, two sons, two daughters, a cop, and a robber.

Rules:
1)Only the cop, the father, and the mother can steer the raft, so one of the two people on the raft must be one of these three.
2)The robber cannot be left on the same side of the river as anyone else if the cop is not also there, he can, however, be on one side of the river alone even if the cop is not there. (this also means only the cop can take him across the river)
3)The mother cannot be on the same side of the river as the son(s) if the father isn't there
4)The father cannot be on the same side of the river as the daughter(s) if the mother isn't there
5)People may only cross the river via the raft, no swimming  ;)
6)The raft can only move across the river if one of the adults is steering it, no ropes pulling it back over unmanned :P

I first heard this from my dad, who heard it from his boss who evidentily spent 3-4 days trying to figure it out, I got it in a couple minutes, let's see how you guys do  :)

edit: I do believe this is the first topic i've ever created, woot!

[Gorak]

cop shoots robber dead,
then fairies the sons over one at a time, then the father, then the daughters, then the mother

[Shade]

heh, apparently I forgot to mention no shooting :P

[Gorak]

ok, so cop starts by taking robber first, but pitches him outta raft half way across leaving him to drown, then procedes as stated in my first post

[pippin the mighty]

The policeman go with the robber first, then they push raft back, then father and sons, then mother and daughters, easy?

[Shade]

The raft can only hold two people, the driver is one of those people, when the father left to ferry the first son across, he'd be leaving the other son alone with the mother, against the rules  :)

[pippin the mighty]

awww bugger...

The cop takes the robber across, leaving the others. Now there is 2 options =)

1). They walk along for a while until they see a bridge =)

2). They phone a bout taxi and get across, simple =)

[bjornredtail]

This is very much like a problem that came up in a CSC class of mine...

1. Cop takes robber across river, leaves him on far bank.
2. Cop returns the raft, empty.
3. Cop takes one of the daughters across the river
4. Cop returns with robber
5. The mother takes the other daughter across the river, returns empty.
6. The Father takes the mother across the river, returns empty.
7. The father takes the first of sons across the river, returns empty.
8. The father takes the second son across the river, returns empty.
9. The father takes the cop across the river.
10. The cop returns empty.
11. The cop takes the robber across the river.

[Shade]

7. The father takes the first of sons across the river, returns empty.
8. The father takes the second son across the river, returns empty.

Nope, good shot, but in 7 and 8 when the father takes the first of the sons across the river and comes back for the second, he leaves the firsts one with the mother

[Alazar is Back]

Ah, it makes my head hurt, im not good at these..... :-\

[Sharptooh]

I know this is kind of bad because as the warning says :

Warning: this topic has not been posted in for at least 120 days.
Unless you're sure you want to reply, please consider starting a new topic.

but this is the spa room and I just figured it out (I think):

1) Cop takes robber across and comes back alone
2) Cop brings one daughter across and takes robber back with him
3) Mother takes a daughter across then goes alone to original bank
4) Mother and Father both go across, Father goes back alone
5) Cop and robber both go across
6) Mother comes back alone and brings father back
7) Father ferries last two sons

Finished!

It took me (about) 5 minutes :D

[Kyrolin Zenyar]

You may have something there, Sharpy... No Google?

[Sharptooh]

You may have something there, Sharpy... No Google?

I don't use Google  :P

But no I didn't use the Internet, I worked it out on paper (and in my head)

[Kyrolin Zenyar]

Wow!