Best First Search
Best First Search is still an instance of general algorithm
Need heuristic score for each search state
MERGE: merge new states in sorted order of score
- I.e. list always contains most promising state first
- can be efficiently done if use (e.g.) heap for list
- no, heaps not done for free in Lisp, Prolog.
Search can be like depth-first, breadth-first, or in-between
- list can become exponentially long