It is a process of computational rules which is designed to operate on some input of data to calculate and return some desired output. (E.g., a computer program that returns a statistical distribution of a list of birthdays, or a sorted list of names, or determines the “best” next play in a hand of blackjack.)
I use “computational” very generally here to describe rules that are rigorously bounded by logic–not rules that require a literal computer. If you were tasked to physically sort people in a queue according to rules and criteria written on a piece of paper, those written instructions could be fairly said to be an algorithm.
Latest Answers