Factorial of a Number

Write a recursive function that computes the factorial of a non-negative integer n, defined as:

• factorial(0) = 1
• factorial(n) = n * factorial(n - 1) for n > 0

Because factorials grow very quickly, return the result as a decimal string (e.g. "120"), not a number, so arbitrarily large results can be represented exactly.

Example: n = 5 returns "120", because 5 * 4 * 3 * 2 * 1 = 120.

You must use recursion (no iterative loops building up the product) to receive full credit from reviewers, although any correct implementation will pass the automated tests.

0 <= n <= 100