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## Can You Beat a Computer At Rock-Paper-Scissors?292

tekgoblin writes "The New York Times has created a game that uses artificial intelligence to outsmart you. It uses a simple game called Rock-Paper-Scissors which is pretty much known by everyone on the planet by now. The computer tries to mimic human reasoning by building on simple rules and statistical averages. So based on the rules of the game and your previous moves, the computer tries to make predictions on your next move. The game has 2 modes, the first being Novice, where the computer learns the game from scratch, and Veteran, where the computer has experience of over 200,000 rounds of previous experience."
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## Can You Beat a Computer At Rock-Paper-Scissors?

• #### Re:I can beat the computer... (Score:5, Informative)

on Wednesday March 09, 2011 @07:53AM (#35428172)
I prefer rock paper scissors lizard spock myself.
• #### Re:I can beat the computer... (Score:4, Informative)

on Wednesday March 09, 2011 @11:59AM (#35430776)

It does not matter whether the computer favors a choice more than the other. Imagine that there is maximal favoritism and the computer just always picks rock. If you play randomly, you will win 1/3 of the time (whenever you happen to randomly pick paper), you will lose 1/3 of the time (idem, scissors), and you will tie 1/3 of the time (idem, rock).

Imagine the computer picks rock X% of the time, paper Y% of the time, scissors in all other instances. Whenever it picks rock, you have 1/3 odds of picking paper and winning. Whenever it picks paper, you have 1/3 odds of picking scissors and winning. Whenever it picks scissors, you have 1/3 odds of picking rock and winning. X * 1/3 + Y * 1/3 + (1 - X - Y) * 1/3 = X/3 + Y/3 + 1/3 - X/3 - Y/3 = 1/3, for all X and for all Y. No strategy can expect to win or lose against a random strategy more than 1/3 of the time in the limit of the number of rounds played.

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