Search algorithms are defined by the node expansion

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Unformatted text preview: → informed search. Search algorithms are defined by the node expansion method: q༇  Breadth-first search q༇  Uniform-cost search q༇  Depth-first search q༇  Depth-limited search q༇  Iterative deepening search. q༇  Bidirectional search 4 9/20/13 When the search graph is not a tree n༆  n༆  n༆  n༆  n༆  Need to avoid repeated states! Happens in problems with reversible operators Examples: missionaries and cannibals problem, sliding blocks puzzles, route finding problems. Detection: compare a node to be expanded to those already expanded. Those are kept in the closed list (aka “explored” set). Increases memory requirements (especially for DFS): bounded by the size of the state space. Breadth-First Search (BFS) n༆  n༆  Expand all nodes at depth d before proceeding to depth d+1. Implementation: queue (FIFO). A C B D E F G Algorithm on pg. 82 in R&N 3rd edition, see pp. 72 & 83 in 2nd Evaluation of BFS n༆  Completeness: q༇  Does it always find a solution if one exists? YES (if shallowest goal node is at some finite depth d) Evaluation...
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This note was uploaded on 02/10/2014 for the course CS 440 taught by Professor Staff during the Fall '08 term at Colorado State.

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