← CS50 Problem Sets

Problem 1

Mario (less comfortable)

Print a half-pyramid of hash-mark blocks, validating a height between 1 and 8.

Background

Recall Mario, the classic 1985 video game wherein the player, as Mario, runs and jumps his way through a mushroom kingdom, collecting coins and avoiding obstacles, all in an effort to save a princess.

screenshot of Mario jumping up a half-pyramid of blocks
Mario jumping up a half-pyramid of blocks.

In this problem, you don’t need to write any code for the game itself. Instead, let’s write some code to print a half-pyramid of blocks like you might see in the game itself, using hashes (#) for blocks, per the below, where the top-left of the game’s screen is deemed to be at the top-left of your terminal window.

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

This particular half-pyramid is eight rows tall and eight columns wide.

Demo

Getting Started

Log into cs50.dev, click on your terminal window, and run:

cd
mkdir mario
cd mario
code mario.py

That creates a new folder called mario, moves into it, and opens a new, empty file called mario.py for you to edit.

Specification

Implement a program, in mario.py, that recreates this half-pyramid using hashes for blocks, wherein the half-pyramid’s height should be a non-negative integer between 1 and 8, inclusive.

  • Prompt the user for the pyramid’s height with input().
  • Convert what the user typed to an integer with int(), and validate it yourself: if it isn’t a valid integer, or is outside the range 1 through 8, print an error (or simply say nothing) and prompt again. Keep prompting until the user gives you a valid height. Converting a non-numeric string like "foo" with int() raises a ValueError if you don’t guard against it, so think about how you’ll catch or avoid that before it crashes your program.
  • Once you have a valid height, generate (with the help of print and one or more loops) the half-pyramid itself.
  • Take care to align the bottom-left corner of your half-pyramid with the left-hand edge of your terminal window, and make sure there’s no trailing whitespace at the end of any row.

How to Test

Confirm that your program behaves as follows.

  • If the user’s input is -1, your program should reject it and prompt the user again for a valid height.
  • If the user’s input is 0, your program should likewise reject it.

  • If the user’s input is 1, your program should output:

    #

  • If the user’s input is 2, your program should output:

    #
##
  • If the user’s input is 8, your program should output an eight-row pyramid like the one shown above.
  • If the user’s input is 9 (or anything greater than 8), your program should reject it and prompt again; only after that should it accept a valid height like 8.
  • If the user’s input is foo (not a number at all), your program should reject it without crashing, and prompt again.
  • If the user presses Enter without typing anything, your program should treat that the same as any other invalid input: reject it and prompt again.

Style and Submission

Run these one at a time, from inside your mario folder.

Check your style:

style50 mario.py

Check your correctness:

check50 cs50/problems/2024/x/sentimental/mario/less

Submit your work:

submit50 cs50/problems/2024/x/sentimental/mario/less

Glossary

  • algorithm — A finite sequence of steps that solves a problem or completes a task. Can be written in English, pseudocode, or code.
  • loop — A statement that runs one or more statements, often repeatedly. (AP calls this iteration.)
  • conditional statement — A statement that controls the flow of execution depending on some condition. Informally, this is usually an if statement, which might include an elif and an else. (AP calls this selection.)
  • boolean expression — An expression whose value is either True or False.