How would you describe recursion in programming?

• A. A technique to avoid function calls
• B. A function calling itself to solve smaller instances of a problem
• C. An iterative approach with loops only
• D. A way to share variables across functions

Answer: (B)

Recursion describes solving problems by having a function call itself with smaller inputs until a simple base case is reached. The essential pieces are a base case that stops the calls and a recursive step that reduces the problem to a smaller version. This lets you express solutions in a natural, straightforward way for problems like factorial, tree traversal, or searching, where each step depends on solving a smaller instance. It's not about avoiding function calls, and it's not limited to loops; a recursive solution can work with or without explicit looping. It also isn't about sharing variables across functions—that's about scope. The defining idea is a function repeatedly calling itself to handle progressively smaller subproblems until the base case stops the process.