Category:Recursion: Difference between revisions

'''Recursion''' is the idea that a function can come to an answer by repeatedly calling itself with new arguments until a "base case" or "end condition" is met. One good example is a [[factorial function]]. The base case for factorial is "0!" (some people like to use 1 or 2, but 0 is OK for instructional purposes). When 5 is sent as an argument to a recursive factorial function, the function does not know the answer right away. All it knows is that 5! = 5 * 4!. So it calls itself to find out what 4! is. This process continues until it gets to 0!, which is 1. Now it has built up a train of answers: 5! = 5 * 4! = 5 * 4 * 3! etc., and it can find the final answer. Other common examples include tree traversal and the [http://en.wikipedia.org/wiki/Minimax min/max algorithm].