I've got a solid understanding of what recursion is and the concept of a base case, but I'm really struggling to take that knowledge and apply it in programming. I often feel overwhelmed with different ways of solving the same problem, especially as I'm learning Data Structures and Algorithms at FreeCodeCamp. When I face a coding problem, I get stuck thinking of various solutions, which makes me hesitant to even sit down at my computer due to the fear of making mistakes. I often find myself feeling inadequate when I see others solving problems online. For example, I came across this snippet on Stack Overflow, and I can't wrap my head around how it translates into a list:
```python
def add_numbers(n):
if not n:
return []
else:
return add_numbers(n - 1) + [n]
print(add_numbers(5))
``` Can someone help me understand how to implement recursion effectively?
3 Answers
When dealing with recursion, it helps to trust that the recursive call will do its job. For your function `add_numbers(n)`, think about it like this: it builds a list up to `n` by trusting that `add_numbers(n - 1)` will return the correct list, then you just add `n` to it. Embrace that trust and you’ll find it much easier to reason about how recursion works!
Recursion can be tricky! The key elements are having a reliable stop condition and making sure your function calls itself correctly when that condition isn't met. A good exercise might be to create a function that flattens nested lists. Once you tackle that, you’ll feel more comfortable with recursion. Just keep in mind that not all programming languages handle recursion the same way, so it’s often used in specific cases like traversing hierarchical data.
You're definitely not alone in struggling with the practical application of recursion! One thing that really helped me was to break it down on paper. For instance, if you call `add_numbers(2)`, it translates to `add_numbers(1) + [2]`, which then leads to `(add_numbers(0) + [1]) + [2]`, and eventually you get to `([] + [1]) + [2]`. Visualizing the calls can clarify how recursion stacks up!
Thanks! That makes it clearer. I’ll give that a try.
Awesome tip! I'll work on the flattening function. Thanks!