Question 1

What other subject do I need to study if I want to major in computer in the future,I'm in high school,for now

Accepted Answer

I would recommend training yourself by implementing various data structures and algorithms that you may find on Wikipedia.  Good data structures to begin researching on include stacks, queues, linked lists and heaps.  The concept of circular arrays will also be helpful.
Also, you should learn about the basic concepts behind Object Oriented Programming (OOP).  You should understand the meaning of levels of abstraction, and be able to use recursion effectively.
Furthermore, you should practice figuring out the order of growth in both space and time of various algorithms just by looking through an implementation of it.
In my experience, a first-term course would spend the first nearly the half of the term teaching the specifics of the programming language that will be used in the majority of the course, as well as the basic concepts behind OOP, and Abstract Data Types (ADTs).  The second term was more about the implementation of ADTs, Dynamic Programming, and further elaboration on OOP.
With this preparation, and if you are able to code quickly and debug effectively, you will have no problem getting an 'A' on that first term course.

Question 2

Are you guys planning for adding database managemeny system?

Accepted Answer

You can try different database and also different courses on the site for the management system.

Question 3

where's the mathematics of computer i didn't found it her !!

Accepted Answer

Generally, understanding computers require probability, algebra, and basic operations with numbers. If go into robotics or AI, you might need more advanced math, 
 In general, the Khan Academy math modules is all you need. 
I always able to program just know basic algebra when I began.

Question 4

how can we write algorithm for reading numbers with in the range using case logic

Accepted Answer

I am assuming that you want to do something like this:
```
switch (number) {
    case range(1, 10):
        // Do something
        break;
}
```
I'm afraid it's impossible in JavaScript, but it is possible to do something similar using if, else if, and else statements.

Question 5

Thank you!

What's the best and average case for searching for an element in a doubly linked list? Theta of N or O of N

Accepted Answer

Best case = you find the element in the first node
Which is both O(1) AND Theta(1)

Average case: 
Each node in a list of size n is equally likely to hold the target. Cost of search for the xth element in the list is x.
So, average cost is: 
Cost = 1/n * (1 + 2 + 3 + ... n)
Cost = 1/n * (n+1)* n/2 = (n+1)/2
Which is both O(n) AND Theta(n)

Question 6

My algorithms class is solely in Python, with the professor explicitly stating that Java is not in the course. In case someone needs some hands-on practice with codes like that or C#, is there any way that some programming languages aside from Java and JavaScript can be referenced and demonstrated in this series of Algorithm lessons?

Accepted Answer

Khan Academy doesn't teach programming languages per se, but there are sites like Code Academy that do. There are also Python 2 lectures from KA on YouTube: https://www.youtube.com/user/khanacademy/search?query=python

Personally I would recommend learning Java for your class, then when you want to do X which you know about in Java, Google "python how to do X". Once you know one language it's very easy to learn Python.

Course: Computer science theory > Unit 1

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