The following is a recursive function:

def countdown(n):
if n == 0:
return
else:
countdown(n - 1)
countdown(5)
In 3-5 sentences, explain the algorithm.

The algorithm is a recursive countdown function. It takes an input, n, and checks if it is equal to 0. If it is, the function returns and terminates. If it is not, the function calls itself with the input n-1. This process continues until n reaches 0, at which point the function returns and terminates. In this specific example, the countdown function is called with an initial value of 5, so it will recursively call itself 5 times before terminating.