Differentiate between recursion and iteration. When would you choose one over the other?

Recursion and iteration are both programming concepts used to repeat certain procedures until a certain condition is met.

1. Recursion: Recursion is a method where the solution to a problem depends on solutions to smaller instances of the same problem. In other words, a function is called by itself until the base condition is met. It uses a divide and conquer strategy. Recursion can be direct (a function calls itself) or indirect (a function A calls another function B, which calls the original function A).

2. Iteration: Iteration, on the other hand, repeatedly executes a series of instructions until a certain condition is met. This is typically implemented with loops, such as for, while, and do-while loops.

When to choose one over the other:

The choice between recursion and iteration can depend on the specific requirements of the problem and the resources available.

1. If the problem can be naturally divided into similar sub-problems, recursion might be a good choice. Recursion can also lead to cleaner and shorter code, which can be easier to understand.

2. However, recursion can be more memory-intensive, as it requires the allocation of memory for each recursive call. If memory is a concern, iteration might be a better choice.

3. Iteration can be more efficient in terms of performance, as it doesn't involve the overhead of repeated function calls like recursion.

4. If the problem is simple and doesn't involve complex sub-problems, iteration can be a straightforward and effective solution.

In conclusion, the choice between recursion and iteration depends on the nature of the problem, the available system resources, and the specific requirements of the task.