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1. Click here for USACO solutions! …just kidding. (You still have until the end of today to take it!)

2. Introduction to Artificial Intelligence • Branch of computer science • Goal of AI – to figure out what to do when you don’t know what to do • “Uncertainty management” • AI program (“intelligent agent”) gets input from environment via “sensors,” affects its environment through “actuators” (output) • Perception action cycle: Loop of sensor input, decisions, actuator output • AI = How to map sensors to actuators

3. Applications of AI • Robotics • Often associated with AI • Translating input from sensors into output (motors, speakers, etc.) • Games • Playing games (e.g. chess) • Making game actors/characters feel more natural • Internet • Web crawlers (search engines), spam filters, recommendations, etc. • Finance • Predicts price fluctuation for stocks, bonds, commodities, etc. • Helps make trading decisions • Medicine • Suggest diagnoses given list of symptoms • Monitor intensive care patients or long-term medication

4. Machine Translation • Utilizes machine learning extensively • Translator is fed many, many examples of already-translated text (such as a news article in two languages) • Builds translation model by figuring out which phrases correspond to which • Ex: “My name is” appears in English wherever “Je m’appelle” does in French • Google Translate does this for 50+ languages • Constantly improved by user feedback

5. Spam Filtering • Also relies on machine learning • Analyzes messages for “spam-like” words/phrases • Figures out which words are most indicative of spam (e.g. “Viagra”) based on past messages • Bayesian probability/inference • Other known “spam-like” qualities • Known spammer IP • Emailed person before? • Addresses recipient by name?

6. PotW - Cow Vegas • In an effort to swindle his cows, Farmer John has devised a (not so) brilliant game to play against Bessie. Bessie, compensating for her bovine intelligence, pays you with milk to write a program that helps play for her. • The game begins with n stacks of coins and mi coins in each stack, and Farmer John graciously lets Bessie go first. If each player takes 1 to k coins from one stack on each turn, and the player who takes the last coin out of all stacks wins, determine who will win assuming optimal play. • Sample Input: 1 2 (one stack, take up to two) 6 (the stack has one coin) • Sample Output: John (either “John” or “Bessie”) • For 15 points, solve the problem for n=1 (1 stack of coins). • For 15 more points, solve the problem for 1 < n < 1,000,000 • All integers in the input are less than 1,000,000 in magnitude.

7. Hints Sample Input #2:                 Sample Output #2: 3 3                                        John 3 6 9 Sample Input #3:                 Sample Output #3: 3 2                                        Bessie 1 1 1 • Try to find a pattern for the basic problem • Use Sprague-Grundy impartial game theory for the extension • Sprague-Grundy theory gives each pile of coins a "nimber" • not necessarily equal to the number of coins • The nimber of a state is equal to the minimum-exclusion of the nimbers of states reachable from the state • Nimber = zero: losing state, otherwise: winning state • XOR nimbers together to combine multiple states (piles) • Consult Google for details • Final solution is actually very simple