CS 470  Artificial Intelligence   Winter 2006,  Instructor:  Jeffrey Horn

HOMEWORK 1:  (program 1):  Uninformed State Space Search in LISP!
 

Handed out/Assigned:	Monday, January 30, 2006
Due:	Friday Feb. 3, 2006

• Thanks for guidance, discussion, and input from everyone (especially Hans!), I've decide we're going with the 3-3 Missionary-Cannibals problem, for which we KNOW there is a solution!
• The problem is defined in problem 7.2 (p. 126) of our textbook, but you can also google it. 
• Keep in mind:
  • Both missionaries and cannibals can operate the boat.
  • Either one or two people can be transported in the boat, including the operator.
  • Being in the boat (on either side) is not "safe".  In other words, if there are two cannibals on the east side, and one missionary in the boat on the east side (let's say trying to pick up one cannibal) then the missionary gets eaten! 
  • Note that the cannibals can never outnumber the missionaries in the boat!  (because of the second point in this list.)
• First, read chapters 7 and 8 on search.
• Then download and install  DR. SCHEME.
• Here are some SCHEME TIPS
• Next take our search engine code for the FWGC problem, here.  
• (And here  is the pseudo code for the uninformed state space search algorithm that our code implements, without loop checking, that is, checking for duplicate (a.ready visited) states).
• (And here  is the pseudo code for the uninformed state space search algorithm WITH LOOP CHECKING).
• Code it up.  Requirements:
• Program:
• Modify the FWGC code.  You will need to figure out an explicit state representation, finite set of operators, definitions of illegal states, and functions that apply each operator to a state to yield a new state.  Keep it simple, keep it short!  There are only two locations in the world, and only three of each of only two kinds of entities.  All that matters for a "safe state" is that cannibals do not outnumber missionaries on either side.  All that matters for a legal move is that there are enough of the entities being moved on the side being moved from.
• Implement uninformed, breadth-first, search. 
• Turn in the source code (SCHEME code, just the fcn defininitions) by email to jhorn@nmu.edu.
• Additional questions:
  
1. Draw me a COMPLETE state space graph for your problem (partial).  (In the state space graph, use your state representation in the labels for the states, and your "move" function for labeling the edges)
2. What is the branching factor (approx. avg.) of your graph?