2. Functions

Remember, the point of the lab is not to complete the tasks. The point of the labs is to understand why the code you have written does what it does. Do not rush through the steps. Take your time and understand everything we are doing. The understanding is important, not just knocking off the tasks.

2.1. Before Kattis

NOTE: If you forget how to do the function stuff, go back to the class notes.

  1. Write a function called add_five_print that takes one integer as a parameter, adds five to it, and then prints out the result. Call the function to verify its correctness. You MUST do this with a function. Below I have given you the code you need to start writing your function.

    def add_five_print(aNum):
    # stuff goes here

  2. Write a function called add_two_nums_print that takes two integers as parameters, adds them together, and then prints out the result. Call the function to verify its correctness. You MUST do this with a function. Below is the code you can use to call the function and test it after you have written/defined the function.

    add_two_nums_print(4, 5)

  3. Write a function called add_three_nums_print that takes three integers as parameters, adds them together, and then prints out the result. Call the function to verify its correctness. You MUST do this with a function.

  4. Write a function called add_two_nums_return that takes two integers as parameters, adds them together, and then returns the result. Effectively this will be identical to add_two_nums_print, but replace the print inside the function (in addition to the one in the name of the function) with return. Run the following code to verify its correctness. What’s return?

    a = add_two_nums_return(4, 5)
print(a)

  5. Call the function add_two_nums_print you wrote in step 3 with the below code. What do you notice? See if you can hack around a little to figure out the difference between print and return (there’s a HUGE difference). Take your time on this one.

    b = add_two_nums_print(4, 5)
print(b)

  6. Write a function called this_is_tough that takes four integers as parameters. This function will ultimately add up the four integers and return the result. HOWEVER, inside this function you are not allowed to use the addition operator (or any arithmetic trick to do addition, like, 5 - (-1*6)), you are required to use the add_two_nums_return written above. You may not use print inside this function (use return). A big hint: You will likely want to call the add_two_nums_return function a total of 3 times. Test that it works with the following code.

    c = this_is_tough(3, 4, 6, 7)
print(c)

2.2. Kattis Problems

Remember, here is magic code we needed last week:

data = input()       # Read a WHOLE, SINGLE line of input
data = data.split()  # Split string into individual pieces
a_var = int(data[0]) # Take string from data[X], convert it to int...
b_var = int(data[1]) # ... And store it in some variable

Warning

The above will only work for certain situations, so you will need to hack this to make it work for specific cases!!!!!!!!!!!!!

Grab a scrap piece of paper to start scratching your ideas down on paper. Paper and pencil is where a lot of programming happens.

Skip any of the following problems if you did them already.

  1. https://open.kattis.com/problems/hello

  2. https://open.kattis.com/problems/carrots

  3. https://open.kattis.com/problems/r2

  4. https://open.kattis.com/problems/faktor (This one is kinda’ a brain teaser. It requires the simplest of math, but it’s not trivial.)

  5. https://open.kattis.com/problems/ladder (Hope you remember your Gr 10 math… if not, good thing Google exists)

  6. https://open.kattis.com/problems/planina (Looks like an INTEGER SEQUENCE (if only there was an On-line encyclopedia).

  7. Go to Kattis and sort the problems by difficulty. Read them, understand the problem, then see if you can figure any out. Most you can’t yet, but still see what you can do and what you CAN’T. Try to figure out why you can’t.