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Homework 2

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Task 1 (20 pts)

Define a GPS-type problem. Give the goal condition, initial conditions, and operations. For each operation, define the action, preconditions, “add” conditions, and “delete” conditions. At least five operators must be defined.

Then, list a sequence of actions (in the correct order) that solve the problem. At least three operators must be used.

Task 2 (15 pts)

Give the sequence of states visited (states evaluated) in a hill-climbing search applied to the Goodale routing problem, starting at Woodruff & Tuttle and ending at Goodale parking lot. You’ll find the goodale-distances.txt file useful.

For each “choice” that the algorithm faces, list the options, the computed scores, and indicate the best choice.

Note, give the sequence of states visited, not just the states that make up the final route. There may (or may not) be some backtracking so the states visited may differ from the route.

Assume hill-climbing does not reconsider previously-visited states.

Your answer should look like this:

Best choice is indicated by a *

- Woodruff & Tuttle
  - choices: Lane & Tuttle (2.318), High & Woodruff (2.103)*
- High & Woodruff
  - choices: ...
...
- Goodale parking lot

Task 3 (25 pts)

Repeat task 2 but for A* search.

Like before, for each “choice” that the algorithm faces, list the options, the computed scores, and indicate the best choice. Since A* may “jump around,” indicate the prior (connecting) state for each choice. Also give the current path cost for each state when that state is visited.

Assume A* does not reconsider previously-visited states.

Your answer should look like this:

Best choice is indicated by a *

Format of arithmetic in parentheses:
  (old path cost + cost of next step + distance from next step to goal = ...)

- Woodruff & Tuttle (cost: 0.000)
  - choices:
    - Woodruff & Tuttle -> Lane & Tuttle (0.000 + 0.170 + 2.318 = 2.488)*
    - Woodruff & Tuttle -> High & Woodruff (0.000 + 0.460 + 2.103 = 2.563)
- Lane & Tuttle (cost: 0.170)
  - choices:
    - Woodruff & Tuttle -> High & Woodruff (0.000 + 0.460 + 2.103 = 2.563)*
    - Lane & Tuttle -> SR-315 & Lane (0.170 + 0.740 + 2.605 = 3.515)
- High & Woodruff (cost: 0.460)
  - choices:
    ...
...
- Goodale parking lot (cost: 2.760)

Task 4 (5 pts)

The Goodale routing problem used road intersection distance to find the routes (when informed search was used). However, this distance (“as the crow flies”) is only one aspect of what makes one route better than another. What other information should we use to find the truly minimal-time route between these two locations?

Task 5 (5 pts)

What are some admissible heuristics for the 8-puzzle problem? Give at least two.

Task 6 (15 pts)

Define breadth-first search in terms of the cost function \(f(s) = g(s) + h(s)\) where \(g(s)\) is the cost of arriving at state \(s\) and \(h(s)\) is the (estimated) cost of getting from \(s\) to the goal state. That is to say, give simple definitions for \(g(s)\) and \(h(s)\) so that the A search algorithm acts like breadth-first search.

Also define depth-first search in terms of \(f(s) = g(s) + h(s)\).

Task 7 (15 pts)

Show a graph of minimax operation for this tic-tac-toe board, where ‘x’ is to make a move (and ‘o’ is the opponent). The graph should look similar to those in the adversarial search notes.

xox
x
oo
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