Mario: Less comfortable

World 1-1

Toward the end of World 1-1 in Nintendo’s Super Mario Brothers, Mario must ascend a right-aligned pyramid of blocks, as shown below.

Let’s recreate that pyramid in C, albeit in text, using hashes (#) for bricks, a la the below. Each hash is a bit taller than it is wide (at least for the font we’re using), so the pyramid itself will also appear taller than it is wide.

       #
      ##
     ###
    ####
   #####
  ######
 #######
########

The program we’ll write will be called mario. And let’s allow the user to decide just how tall the pyramid should be by first prompting them for a positive integer between 1 and 8, inclusive.

Here’s how the program might work if the user inputs 8 when prompted:

$ ./mario
Height: 8
       #
      ##
     ###
    ####
   #####
  ######
 #######
########

Here’s how the program might work if the user inputs 4 when prompted:

$ ./mario
Height: 4
   #
  ##
 ###
####

Here’s how the program might work if the user inputs 2 when prompted:

$ ./mario
Height: 2
 #
##

And here’s how the program might work if the user inputs 1 when prompted:

$ ./mario
Height: 1
#

If the user doesn’t, in fact, input a positive integer between 1 and 8, inclusive, when prompted, the program should re-prompt the user until they cooperate:

$ ./mario
Height: -1
Height: 0
Height: 42
Height: 50
Height: 4
   #
  ##
 ###
####

How to begin? Let’s approach this problem one step at a time.

1. Prompting for Input

Let’s first write only the C code that prompts (and re-prompts, as needed) the user for input.

Specifically, add code in mario.c in such a way that it prompts the user for the pyramid’s height, storing their input in a variable, re-prompting the user again and again as needed if their input is not a positive integer between 1 and 8, inclusive. Then, just print the value of that variable, confirming (for yourself) that you’ve indeed stored the user’s input successfully, a la the below:

$ ./mario
Height: -1
Height: 0
Height: 42
Height: 50
Height: 4
OK: 4

Hints

• Recall that you can print an int with printf using %i.
• Recall that you can get an integer from the user with get_int.
• Recall that get_int is declared in the cs50.h library.
• Recall that we prompted the user for a positive integer in class via positive.c (link).

2. Building the Opposite

Now that your program is (hopefully!) accepting input correctly, it’s time for another step.

It turns out it’s a bit easier to build a left-aligned pyramid than right-, like this:

#
##
###
####
#####
######
#######
########

So let’s build a left-aligned pyramid first and then, once that’s working, right-align it instead!

Modify mario.c so that it no longer simply prints the user’s input but instead prints a left-aligned pyramid of that height.

Hints

• Keep in mind that a hash is just a character like any other, so you can print it with printf.

• In C we have a for loop, where you can iterate some number of times. Perhaps on each iteration, i, you could print that many hashes?

• You can actually “nest” loops, iterating with one variable (e.g., i) in the “outer” loop and another (e.g., j) in the “inner” loop. For instance, here’s how you might print a square of height and width n, below. Of course, it’s not a square that you want to print for this problem!

  for (int i = 0; i < n; i++)
  {
      for (int j = 0; j < n; j++)
      {
          printf("#");
      }
      printf("\n");
  }
  

3. Right-Aligning with Dots

Let’s now right-align that pyramid by pushing its hashes to the right by prefixing them with dots (i.e., periods), a la the below.

.......#
......##
.....###
....####
...#####
..######
.#######
########

Modify mario.c in such a way that it does exactly that!

Hint

Notice how the number of dots needed on each line is the “opposite” of the number of that line’s hashes. For a pyramid of height 8, like the above, the first line has just 1 hash and thus 7 dots. The bottom line, meanwhile, has 8 hashes and thus 0 dots. Via what formula (or arithmetic, really) could you print the right number of dots and hashes on each line?

Test Your Code

Does your code work as prescribed when you input:

• -1 (or other negative numbers)?
• 0?
• 1 through 8?
• 9 or other positive numbers?
• letters or words?
• no input at all, when you just hit Enter?

4. Removing the Dots

All that remains now is a finishing flourish! Modify your program so that it prints spaces instead of those dots!

How to Test Your Code

Execute the below to evaluate the correctness of your code using check50. But be sure to compile and test it yourself as well!

check50 scienceacademy/problems/2024ap/mario/less

Execute the below to evaluate the style of your code using style50.

style50 mario.c

How to Submit

Execute the below:

submit50 scienceacademy/problems/2024ap/mario/less