What is the purpose of the base case in recursion?

The base case in recursion serves a critical role in providing a direct solution to the simplest instance of a problem. When a recursive function is defined, it typically breaks down a complex problem into smaller subproblems, which are easier to solve. The base case is the condition that specifies when the recursion should stop and provide an answer without further recursive calls.

For example, in a recursive factorial function, the base case would identify the factorial of 0 as 1 (0! = 1). This allows the function to return a direct answer rather than continuing to call itself indefinitely. Without a base case, the recursion would proceed infinitely, leading to a stack overflow or unresolvable loop. Establishing the base case ensures that the recursive function can terminate, providing a solid foundation for building solutions to larger instances of the problem through the recursive calls.