mpotd
okay so a coworker hits me with the math problem of the day. you've identified a traitor in a city of 4 million people. but you're a super spy. and you don't want to blow your cover. the only way to communicate with the authorities is by dropping a bag of tokens in a laundry chute. the tokens are unique - dog, car, iron, cannon, etc. the bag holds exactly six tokens. how many different tokens do you need in order to identify the traitor? give me an algorithm that efficiently maps the traitor's id to a set of tokens. and vice versa.