SLOG 9

This week I think I have to look back and see if I agree with my early ideas. I visited SLOG 6，and found that my comprehension on the depth of a node was totally wrong. It should be counted from the root to the node but not from the node to the leaf. Also, I visited SLOG3, and I think I have to supplement something on it. In SLOG3 I talked about the concept of Recursion, but I didn’t mention the way to write a recursion. There are quite a lot of ways to write recursion, and we have to decide which one to use. I can just make some examples to lead.

Suppose we have a nested list [3，[5，6，7],[2，[1]],2], and we want to sum the data inside. By calculating we can easily get the answer, but it is not working for a computer. So we need to write codes by using recursion. One of the skills to write a correct recursion is to find the final thing we operate. In this example, we can tell that those numbers are the so-called final things. So we start the code like this:

def   nested_list(L):

     if isinstance(L,int):

         return L

Then we have to consider about the core of the problem: the way to call the function itself.

If we call [nested_list(x) for x in L] for just once, it means we check if 3，[5，6，7],[2, [1]], 2 are int. If true, then put it into a blank list. If we call it twice, then 3，5，6，7，2，2 are in the list, and there will only be a list [1] still not there. Call it again, we have all the things in the list. All we have to do here is to sum the list. So we can write a code like this:

return sum ([nested_list(x) for x in L]).

To make it clearer, I put the codes together:

def   nested_list(L):

     if isinstance(L,int):

         return L

else:

    return sum ([nested_list(x) for x in L])

I also read the slogs written by some of my classmates, and their idea helps me a lot. Plenty of my classmates are puzzled on testing as well, and I found that we all struggled about the Minimax of the assignment2. Object Oriented Design is not a common problem, since it is the base of CSC148. But I think the easier it is, the more careful we should be. The easiest part is always the part which makes most people careless.