CS156 Spring 2015Practice Midterm

To study for the midterm I would suggest you: (1) Know how to do (by heart) all the practice problems. (2) Go over your notes at least three times. Second and third time try to see how much you can remember from the first time. (3) Go over the homework problems. (4) Try to create your own problems similar to the ones I have given and solve them. (5) Skim the relevant sections from the book. (6) If you want to study in groups, at this point you are ready to quiz each other. The practice midterm is below. Here are some facts about the actual midterm: (a) It is closed book, closed notes. Nothing will be permitted on your desk except your pen (pencil) and test. (b) You should bring photo ID. (c) There will be more than one version of the test. Each version will be of comparable difficulty. (d) One problem (less typos) on the actual test will be from the practice test.

1. Explain the PEAS task environment description.
2. Consider the 8-puzzle. For each of the following show an example search tree where you have expanded at least three nodes: (a) Breadth First Search, (b) bidirectional search, (c) `A^star`-search. Say why you expanded the nodes you did and what heuristics you used if any.
3. Write a short Python class for maintaining a tic-tac-toe board. You should at least have a method for adding a piece to a board and printing out a board. Your method for adding a piece to the board should check if the square is already occurpied and if it is, throw an exception.
4. Give an example of an admissible heuristic for the 8-puzzle problem which could be used in `A^star` search for a solution. Show why it is admissible.
5. What is stochastic hill climbing? What is random hill climbing with restarts? What is `k`-local beam search?
6. Give the minimax algorithm. How would it be modified if one had a game for which one could not fully expand the game tree? Draw a game tree with a beta-cut and explain why it is a beta-cut.
7. Define and give an example of each of following properties of CSPs: (a) Node Consistency, (b) Arc Consistency, (c) Path Consistency.
8. Give an example CSP in which the MRV heuristic and the degree heuristic would choose different variables. Explain what CSP backjumping is.
9. Express the following in propositional logic: Square `i,j` has a breeze if and only if one of four adjacent squares has a pit.
10. Give a resolution refutation of the following clauses: `{a,bar(b)}, {bar(a)}, {bar(c),b}, {c}`.