IQ Test Puzzle

EDIT: A less lazy comment--SmallCampus.net that the game links to is a Hong Kong website, which has a collection of puzzles. I still can't find a reference to this being a Japanese job test though.

EDIT2: And, here's the real source. http://www.smallcampus.net/htmlcontent.php?channel=maths_gam... It's a brain teaser for elementary school children.

P+T > P > P+S > P+T > F+S > F > F+M > M > P+T > F > F+M > M > M+D > P+T > P+D > P > P+T

Where P=policeman T=thief S=son F=father M=mother D=daughter.

It helped me to approach this as some kind of machine, or a universe with weird physics - from there you can establish some basic operations which are then easy to combine into the whole solution.

When there is a free shore or one person on a shore the cop can serve as an agent of motion as he's only inhibited by the crim, who can be put in that free space. A free cop will let you deal with one of the kids in the problem, the parent can then deal with the remaining kid themselves or the cop can. A mother/father boat shuttle on either side of a cop/crim transport shifts the criminal problem over and allows the cop's magic to be used again, but from the opposite shore.

The cop ferries criminal over to opposite side. He then returns and ferries a boy over and bringing the criminal back. This exploits cop/crim rule by putting the crim alone on a bank and thus "freeing" up the cop's capacity as a coxswain to get the boy over.

Father goes over with next boy. Both boys on the other shore now, but nobody else is there so the father is thus freed up.

They use this freedom to get the boat back by the father returning, and then the mother ferrying him back, and returning with the boat alone.

The cop goes over with the criminal, both stay.

The father returns the boat, goes back with the mother and she comes back alone. This is the same as the previous mother/father move, but it's enabled the cop and crim to come over.

The mother then takes a girl over and stays there with her. Exploiting the fact that there is only one girl left on the original shore and thus she is alone and no rules are violated.

The cop and the criminal come back.

The cop takes the remaining girl over, leaving the criminal alone.

The cop fetches the criminal in a final move.

Like many word problems it is beset with confusions via hidden assumptions. The assumption that children can't be trusted with their parents and a cop is to be trusted with children more than the parents is weird. Unsupervised children are apparently safer than with their parents too. The assumption that the criminal is dangerous to unprotected family members, through theft or violence, but won't run away when left alone clouds the solution as you intuitively don't want to leave the criminal alone even though the rule is stated only in relation to family members.

http://www.cs.utexas.edu/users/EWD/transcriptions/EWD12xx/EW...

> The Mother cannot stay with any of the sons, without their Father's presence

This is a bit disturbing.