04-18 Lecture Slides (Final)

G 5 disk toh puzzle missionaries cannibals heuristic

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Unformatted text preview: Initial state? Goal state? Operators? 4 4/18/13 Simplified Problem Space for Missionaries & Cannibals MMM MMM KKK KKK MMà༎ MMM MMM KKK KKK KKà༎ Initial State MKà༎ MMM MMM KKK KKK MMM MMM KKK KKK ß།M MMM MMM KKK KKK KKà༎ ß།K MMM MMM KKK KKK MKà༎ MMM MMM KKK KKK MMM MMM KKK KKK ZAPS #10: Missionaries & Cannibals n༆  n༆  Well- defined or ill- defined? Is using an algorithm an efficient way to solve this problem? General Problem Solving Heuristics n༆  There are commonly used problem solving heuristics (1) Generate and test (trial and error) (2) Hill climbing (3) Means- ends analysis (4) Working backwards n༆  Different heuristics can be applied to the same problem ¨༊  Examples: Tower of Hanoi (TOH) puzzle; Missionaries & cannibals puzzle n༆  The ease and effectiveness of applying a particular heuristic depends on the nature of the problem ¨༊  Selecting an appropriate heuristic is crucial for effective problem solving 5 4/18/13 Heuristic 1: Generate and Test (Trial and Error) n༆  Trying a variety of solutions one at a time and eliminating those that do not work ¨༊  Example: n༆  n༆  You forgot the password for an account you haven’t used for a while, so you try your current passwords one by one Its effectiveness depends on the range of possible solutions ¨༊  It is effective only when the number of possible solutions are limited ¨༊  It may not be appropriate for highly complex problems (e.g., 5- disk TOH puzzle; missionaries & cannibals) Heuristic 2: Hill Climbing n༆  Trying to always move closer to the goal state Multiple operators = choose the one that moves you in the direction of the goal state ¨༊  Example: ¨༊  n༆  n༆  Solving the TOH puzzle by always trying to move disks from left to right Useful and non- demanding ¨༊  People often spontaneously adopt it Heuristic 2: Hill Climbing n༆  It may not work for problems that require temporarily moving away from the goal state ¨༊  Example: n༆  Trying to solve Rubik’s cube one face (or one color) at a time n༆  Moving a disk in a backward...
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This note was uploaded on 02/18/2014 for the course PSYC 2145 taught by Professor Cheriking during the Spring '07 term at Colorado.

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