River IQ Test

The River IQ Test (aka River IQ Game) is a mental puzzle. The name originates as it supposedly is given as an IQ test to job applicants in China. The puzzle is in Chinese, but can be completed with ease once the rules have been translated.

The aim

The object is to get everyone (father, two sons, mother, two daughters, police officer and thief) from one side of the river to the other whilst adhering to certain rules.

The rules

The following rules apply:
# At most two persons on the raft at any time
# The father cannot stay with any of the daughters without their mother's presence
# The mother cannot stay with any of the sons without their father's presence
# The thief (striped shirt) cannot stay with any family member if the police officer is not there
# Only the father, the mother and the police officer know how to operate the raft

olution

Initially the puzzle seems daunting with a large number of possible moves, however there is in fact very little choice as the wrong moves prevent any further moves. There are only two possible sequences of moves that will accomplish the goal in the least number of steps.{| class="wikitable"
-! Move No.! Across! Back
-
1
Police Officer, Thief
Police Officer
-
2
Police Officer, Daughter 1
Police Officer, Thief
-
3
Mother, Daughter 2
Mother
-
4
Father, Mother
Father
-
5
Police Officer, Thief
Mother
-
6
Father, Mother
Father
-
7
Father, Son 1
Police Officer, Thief
-
8
Police Officer, Son 2
Police Officer
-
9
Police Officer, Thief

Application to solve the problem

There is sample application written by Mortaza Doulaty in Visual Basic .NET 2005 that solves this problem and shows the answers (although the attached screenshot shows an incorrect answer).

You can download the source code from the programmer's web site:http://www.mrt-web.com/Public/RiverCrossingProblem.zip

ee also

*Transport puzzle
*River crossing puzzle
*Fox, goose and bag of beans puzzle
*Missionaries and cannibals problem

External links

* [http://www.riveriqtest.com Play River IQ Test Online]
* [http://freeweb.siol.net/danej/riverIQGame.swf Online Macromedia Flash version]