This lesson focuses on Simple Recursion in Practice. Recursion is a foundational concept in computer science and an essential skill for any programmer. It allows you to simplify complex problems by solving smaller instances of the same problem within the solution. Though initially challenging, mastering recursion helps make code more elegant and readable.

Let’s look at a classic example of recursion: calculating the factorial of a number. The factorial of a number n (denoted as n!) is the product of all positive integers less than or equal to n.

Recursively, we can think of the factorial of n as the number n multiplied by the factorial of n - 1. This pattern continues until n reaches 0, at which point we return 1 (since the factorial of 0 is 1 by definition), ending the recursion.

Here’s how it might look:

Ruby
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1def factorial(n)
2  # Base case: factorial of 0 is 1
3  if n == 0
4    1
5  # Recursive case: multiply n by factorial of n-1
6  else
7    n * factorial(n - 1)
8  end
9end
10
11# Example usage
12puts factorial(5)  # Outputs 120

In this function, the base case handles when n reaches 0, while the recursive case calls the function itself with n - 1 until reaching that base case.

Recursion is widely used in areas like algorithms and data structures. This introduction is just the beginning. Now, let’s solidify your understanding with practice exercises that build upon this foundation and help you become more comfortable with recursive thinking. Dive in and see recursion in action!