Best-first search is a search algorithm which explores a graph by expanding the most promising node chosen according to a specified rule.

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Presentation transcript:

Best-first search is a search algorithm which explores a graph by expanding the most promising node chosen according to a specified rule.

 This specific type of search is called greedy best- first search or pure heuristic search.  Efficient selection of the current best candidate for extension is typically implemented using a priority queue.  The A* search algorithm is an example of best- first search, as is B*.  Somtimes best-first search doesn’t find the “best” (shortest/longest/cheapest) path to the target!

 open = initial state  while open != null do  1. Pick the best node on open.  2. Create open's successors  3. For each successor do:  a. If it has not been generated before: evaluate it, add it to OPEN, and record its parent  b. Otherwise: change the parent if this new path is better than previous one.  done

Depth-first search (DFS) is an algorithm for traversing or searching tree or graph data structures. One starts at the root (selecting some arbitrary node as the root in the case of a graph) and explores as far as possible along each branch before backtracking.