complexity & sorting

We had learnt complexity & sorting at CSC108, but the content was not going that complex, just some warm-up. After learning recursion, it's better for us to understand how sorting works, at least for me. In the furture, the best way to test a programmer is to see his code's effiiency, those sorting methods show us how to solve question in different way and different time effiiency.

E3 and A2

A lot recursion... which makes me so frustrating. However, this topic really needs practice to understand it well. On E3 Part 1, I was trying to make a class to do it, but it did not go well. After reading the handout thousands of times, I realized it was much more easier to consider it as a list instead of tree, and then problems solved. I think I do need more practice for recursion, there is actually something like formula that could make the recursion problem much more easier, which was ementioned in the handout couple times, Starting from the small problems, and then try larger one. 

As for A2, I guess A2 part1 did not go well, I think I might get confused by the new concept Regular expressions. Gonna work harder on this.