HW 2 Answer Key
Topics: heuristic search, heuristics, memory bounded search, local search, adversarial search
1. One of these things is just like the other
In class we said that, while there might be hundreds of search algorithms, they're really just variations of a few
core ideas. For example, greedy best-first search acts just like depth-first search when the heuristic h(n) = -1 *
depth. In the following questions, explain under what circumstances one algorithm behaves just like another
one. Short answers are fine.
a. When does uniform cost search behave like breadth-first search?
All costs are the same (all costs are 0 is a minor error, = 3pts)
b. When does A* behave like uniform cost search?
When h(n)=0
c. When does local beam search behave like hill climbing?
When the number of beams = 1
d. When does stochastic hill climbing (essentially) behave like hill climbing?
When the values of all options is the same
e. When does simulated annealing behave (from the very start) like first choice hill climbing?
Either:
1. When T=0
2. When all options have a positive value
2. Franken-Algorithms
Making an algorithm is often like making a recipe - mix one part of algorithm A, one part algorithm B, etc.
Many algorithms are just combinations of simpler algorithms or a simple algorithm and a simple idea (e.g.,
depth-limited depth-first search is depth-first search + a depth limit). For the following algorithms, list which
algorithms or ideas (features, etc.) were used to make the following. There should be two parents for each. Short
answers are fine.
NOTE: We spent an entire class discussing this
a. A*
uniform cost and greedy best first search

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