CSC148 SLOG for week9

The term test took place this week as scheduled. Although I thought I was fully prepared, it was still quite challenging for me. This test covered trees, recursion and LinkedList all of which are difficult concept in CSC148. I went over those topics thoroughly before the exam, however, it still took me long time to solve a practical problem during the test. Taking recursion as an example, it’s hard to figure out a perfect recursive step since you have to consider all situations that are possible to occur and try to express them in a concise way. I’ll try my best to master those concepts and use them smoothly before the final exam.

CSC148 SLOG for week8

Busy preparing for the CSC148's term test and another test, so I will update my impression next week. Sorry!

CSC148 SLOG for week7

This week I want to make a summary of recursion(and I choose this topic to be graded, thanks).

What is recursion?

Briefly speaking, it’s a function calls itself. As we’ve learned in class, any problem solved by recursion can also be solved by iteration. However, using recursion is a wise choice for some complex problem since it always makes the code shorter.

A simple but representative example of recursion:

def recursion(n):

      if n == 1:

          return 1

      else:

          return n * recursion(n - 1)

It’s not difficult to find that this is a function for factorial. The function will automatically call itself until n equals 1 which stops the process of factorial. Since this question is not that hard, we can handle it using while loop, too. But when we facing a complicated question, we may need using loop under loop and, without doubt, it is more likely to make a mistakes. Using recursion, we just need to divide a problem into two parts, basic cases and sub-problems. Basic case is always zero or empty string/list(which is easy to solve) and for the sub-problems, the function calls itself until the basic case occurs. For example, we need recursion when writing functions with nested list. The function will run itself again if it encounter another list and stop when there is no more sub-list, solving the question layer by layer. So recursion is an essential tool for computer scientists when the problem involves an object within another object, such as some Trees question. 

Having eliminated the unnecessary code, recursion solves the most problems in an efficient and elegant way. Although it takes some time to grasp this brilliant method, you will find it’s all worthwhile after mastering it.