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 o “Uncertainty management” o AI program (“intelligent agent”) gets input from environment via “sensors,” affects its environment through “actuators” (output) o Perception action cycle: Loop of sensor input, decisions, actuator output o AI = How to map sensors to actuators

3. Applications of AI Robotics o Often associated with AI o Translating input from sensors into output (motors, speakers, etc.) Games o Playing games (e.g. chess) o Making game actors/characters feel more natural Internet o Web crawlers (search engines), spam filters, recommendations, etc. Finance o Predicts price fluctuation for stocks, bonds, commodities, etc. o Helps make trading decisions Medicine o Suggest diagnoses given list of symptoms o 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) o Builds translation model by figuring out which phrases correspond to which o Ex: “My name is” appears in English wherever “Je m’appelle” does in French Google Translate does this for 50+ languages o Constantly improved by user feedback

5. Spam Filtering Also relies on machine learning Analyzes messages for “spam-like” words/phrases o Figures out which words are most indicative of spam (e.g. “Viagra”) based on past messages o Bayesian probability/inference Other known “spam-like” qualities o Known spammer IP o Emailed person before? o 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 m i 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 o Sprague-Grundy theory gives each pile of coins a "nimber" not necessarily equal to the number of coins o The nimber of a state is equal to the minimum-exclusion of the nimbers of states reachable from the state o Nimber = zero: losing state, otherwise: winning state o XOR nimbers together to combine multiple states (piles) o Consult Google for details Final solution is actually very simple