2.3 Mario

What to do

Toward the end of World 1-1 in Nintendo’s Super Mario Bros., Mario must ascend right-aligned pyramid of bricks, as in the below.

screenshot of Mario jumping up a right-aligned pyramid

In a file called mario.c in a folder called mario, implement a program in C that recreates that pyramid, using hashes (#) for bricks, as in the below:

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

But prompt the user for an int for the pyramid’s actual height, so that the program can also output shorter pyramids like the below:

  #
 ##
###

Re-prompt the user, again and again as needed, if their input is not greater than 0 or not an int altogether.

How to Submit

  • Click and accept the Homework Link on the homework 2 main page.
  • Complete each assignment for week 2 in the Github Codespaces environment.
  • Save and click β€œCommit changes”.
  • The autograder runs automatically; see the Actions tab for feedback.# this version of Mario (less)

Advice

  • Recall that you can get an int from a user with get_int, which is declared in cs50.h.
  • Recall that you can print a string with printf, which is declared in stdio.h.

Write some code that you know will compile

Even though this program won’t do anything, it should at least compile with make!

#include <cs50.h>
#include <stdio.h>

int main(void)
{

}

Write some pseudocode before writing more code

If unsure how to solve the problem itself, break it down into smaller problems that you can probably solve first. For instance, this problem is really two problems:

  1. Prompt the user for the pyramid’s height
  2. Print a pyramid of that height

So write some pseudcode as comments that remind you to do just that:

#include <cs50.h>
#include <stdio.h>

int main(void)
{
    // Prompt the user for the pyramid's height

    // Print a pyramid of that height
}

Convert the pseudocode to code

First, consider how you might prompt the user for the pyramid’s height. Recall that a do while loop is helpful when you want to do something at least once, and possibly again and again, as in the below:

#include <cs50.h>
#include <stdio.h>

int main(void)
{
    // Prompt the user for the pyramid's height
    int n;
    do
    {
        n = get_int("Height: ");
    }
    while (n < 1);

    // Print a pyramid of that height
}

Second, consider how you might print a pyramid of that height, from top to bottom. Notice how the first row should have one brick, the second row should have two bricks, and so on. Odds are you’ll want a loop, as in the below, even if not (yet!) sure what to put in that loop. So add some more pseudocode as a comment for now:

#include <cs50.h>
#include <stdio.h>

int main(void)
{
    // Prompt the user for the pyramid's height
    int n;
    do
    {
        n = get_int("Height: ");
    }
    while (n < 1);

    // Print a pyramid of that height
    for (int i = 0; i < n; i++)
    {
        // Print row of bricks
    }
}

How to print that row of bricks? Well, wouldn’t it be nice if there were a function called print_row that could do just that? Let’s suppose that there is:

#include <cs50.h>
#include <stdio.h>

void print_row(int bricks);

int main(void)
{
    // Prompt the user for the pyramid's height
    int n;
    do
    {
        n = get_int("Height: ");
    }
    while (n < 1);

    // Print a pyramid of that height
    for (int i = 0; i < n; i++)
    {
        // Print row of bricks
    }
}

void print_row(int bricks)
{
    // Print row of bricks
}

We could then call that function from main, as in the below:

#include <cs50.h>
#include <stdio.h>

void print_row(int bricks);

int main(void)
{
    // Prompt the user for the pyramid's height
    int n;
    do
    {
        n = get_int("Height: ");
    }
    while (n < 1);

    // Print a pyramid of that height
    for (int i = 0; i < n; i++)
    {
        // Print row of bricks
        print_row(i + 1);
    }
}

void print_row(int bricks)
{
    // Print row of bricks
}

Why i + 1, though?

Let’s now implement print_row:

#include <cs50.h>
#include <stdio.h>

void print_row(int bricks);

int main(void)
{
    // Prompt the user for the pyramid's height
    int n;
    do
    {
        n = get_int("Height: ");
    }
    while (n < 1);

    // Print a pyramid of that height
    for (int i = 0; i < n; i++)
    {
        // Print row of bricks
        print_row(i + 1);
    }
}

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

Why the \n at the end, though?

Unfortunately, this code prints a left-aligned pyramid, but you need a right-aligned one! Perhaps we should print some blank spaces before some of the bricks, to move them to the right? Let’s change print_row as follows so that it can print both:

#include <cs50.h>
#include <stdio.h>

void print_row(int spaces, int bricks);

int main(void)
{
    // Prompt the user for the pyramid's height
    int n;
    do
    {
        n = get_int("Height: ");
    }
    while (n < 1);

    // Print a pyramid of that height
    for (int i = 0; i < n; i++)
    {
        // Print row of bricks
    }
}

void print_row(int spaces, int bricks)
{
    // Print spaces

    // Print bricks
}

Some pseudocode now remains in both main and print_row, so that we leave to you!

And consider whether you could factor out some of the code in main to a get_height function, too, that returns the int you need!

Note this walkthrough specifies your program should prompt the user for a pyramid’s height and re-prompt if the user inputs a value less than 1 or greater than 8. The specification only requires you to re-prompt the user if they input a value less than 1.

Tests

Does your code work as prescribed when you input:

  • -1 or other negative numbers?
  • 0?
  • 1 or other positive numbers?
  • letters or words?
  • no input at all, when you only hit Enter?

How to Submit

  • Click and accept the Homework Link on the homework main page for this week.
  • Complete each assignment for this week in the Github Codespaces environment.
  • Save and click β€œCommit changes”.
  • The autograder runs automatically; see the Actions tab for feedback.