Outputs of a program

Question

I am new to programming and I would like to know how to solve questions like this. I was told to expect questions like this on the exam. Can someone please tell me how I would go about solving something like this? Thanks.

x = 0
for num in range(5):
    if num % 2 == 0:
        x = x + 2
    else:
        x = x + 1
        print(x)

Answer 1

You need to work on a skill which is to "be the compiler", in the sense that you should be able to run code in your head. Step through line by line and make sure you know what is happening. In you code example, you have for num in range(5) means you will be iterating with num being 0,1,2,3 and 4. Inside the for loop, the if statement num % 2 == 0 is true when num/2 does not have a remainder (how % mods work). So if the number is divisible by 2, x = x+2 will execute. The only numbers divisible by 2 from the for loop are 0,2 and 4. so x=x+2 will execute twice. The else statement x = x +1 runs for all other numbers (1,3) which will execute 2 times.

Stepping through the for loop:

num = 0 //x=x+2, x is now 2
num = 1 //x=x+1, x is now 3, print(x) prints 3 
num = 2 //x=x+2, x is now 5
num = 3 //x=x+1, x is now 6, print(x) prints 6
num = 4 //x+x+2, x is now 8

Therefore the answer is that 3 and 6 will be printed

Answer 2

In my opinion,

1. Whatever language you are using, you need to learn some common elements of the modern programming languages, such as flow-control (if...else in your case), loop(for, in your case)

2. Some common used functions, in your case, you need to what does range do in Python, docs.python.org is a good place for you.

As you are new to programming, you can go with the flow in you mind or draw it on the paper.

1. Using x to store our final result

2. loop through every item in [0, 1, 2, 3, 4] <- range(5)

   a. if the number is divisible by 2 then increase x by adding 2 to it.

   b. else increase x by adding 1 and print it out

So the result would be :

3

6