CS50 Intro to Computer Science

WEEK 0 - Scratch

Problem Set 0

Scratch - CS50x 2022

Requirements:

• Your project must use at least two sprites, at least one of which must not be a cat.
• Your project must have at least three scripts total (i.e., not necessarily three per sprite).
• Your project must use at least one conditional, at least one loop, and at least one variable.
• Your project must use at least one custom block that you have made yourself ( via Make a Block), which must take at least one input.
• Your project should be more complex than most of those demonstrated in lecture (many of which, though instructive, were quite short) but it can be less complex than Oscartime and Ivy’s Hardest Game.

Once finished with your project, select File > Save now one last time. Then select File > Save to your computer and keep that file so that you can submit it. If prompted by your computer to Open or Save the file, be sure to Save it.

Result: Skelly's Hell Loop

WEEK 1 - C

Windows

For local setup download CS50 library:

https://github.com/cs50/libcs50

Include it in your CMakeLists.txt file

add_executable(CS50_22_Intro_to_CS
        "Week 2/hello_world.c"
        "Week 2/libcs50-10.1.1/src/cs50.c")

Linux

$ curl -s https://packagecloud.io/install/repositories/cs50/repo/script.deb.sh | sudo bash
$ sudo apt-get install libcs50

Problem Set 1

Hello

Hello - CS50x 2022

Requirements:

• Get user input
• join input into output string
• output "hello, {input}"

Mario (More)

Mario - CS50x 2022

Requirements: Program takes input integer between 1 and 8, inclusive Outputs pyramid corresponding to Mario game

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

Height must be the amount entered by user

Credit

Credit - CS50x 2022

Requirements:

• Get user input long int
• Validate checksum - Luhn’s Algorithm
• Check if card validates to corresponding card rules:
  • // AMEX: 15 digit, 34 || 37
  • // MASTERCARD: 16 digit, starts with 51-55
  • // VISA: 13 || 16, starts with 4

WEEK 2 - Arrays

LAB 2

Lab 2: Scrabble - CS50x 2022

Requirements:

• Fill in the logic for compute_score function
  • Uses variable named POINTS array for assigning score for each letter in word
  • All characters that are not letters are worth 0 points
  • Lower- and uppercase are worth the equal amount of points
  • Function returns score result for the word provided as argument
• Main function needs to provide output depending on players scores
  • Player 1 wins!
  • Player 2 wins!
  • Tie!

Problem Set 2

Readability

Readability - CS50x 2022

Requirements:

• Get user input text
• Count the letters in the text
  • Only letters - no numbers, punctuation or other symbols
  • function name count_letters
    • takes argument string text
    • returns int letter_count
• Count words in the text
  • Word is any sequence of characters separated by space
  • function name count_words
    • takes argument string text
    • returns int word_count
• Count sentences in the text
  • Sentence ends with ., !, ?
  • function name count_sentences
    • takes argument string text
    • returns int sentence_count
• Calculate 100 word averages
  • count/nr_words * 100
• Calculate grade using formula
  • index = 0.0588 * letter_avg - 0.296 * sentence_avg - 15.8
• Output result
  • if grade equal or higher than 16 - "Grade 16+"
  • if grade lower than 1 - "Before Grade 1"

Substitution

Substitution - CS50x 2022

Requirements:

• Provide key via command-line argument
  • If key not long enough - "Key must contain 26 chars"
  • If the key is missing or too many keys - "Usage: ./substitution key"
  • Validate key
    • Only letters
    • No repeating letters
• Encrypt provided message using the key
  • Prompting for - "plaintext: "
• Return result
  • Prefixed by - "ciphertext: "
  • Case remains same after encryption
  • Only replace alphabetical characters

WEEK 3 - Algorithms

LAB 3

Lab 3: Sort - CS50x 2022

Requirements:

• Run three provided compiled C programs sort1, sort2, sort3
• Determine which sorting algorithm they are running
• Provide answers to answers.txt file

Problem Set 3

Plurality

Plurality - CS50x 2022 Requirements:

• Complete vote function
  • single argument, string name(Candidate name)
  • if a match, increase corresponding vote count
  • returns true or false
• Complete print_winner function
  • print out name of the candidate who received the most votes in the election
  • in case of tie print out names of each winning candidates, each on separate line

Tideman

Tideman - CS50x 2022

• Complete vote function
  • function takes arguments int rank, string name, array ranks
  • updates the ranks array to indicate voter preference
    • ranks[i] represents user i'th preference
  • return true or false
• Complete the record_preference function
  • called for each voter once
  • takes argument array ranks
  • should update global preferences array to add current voter preference
    • preference[i][j] - voters who prefer i candidate over candidate j
• Complete the add_pairs function
  • should add the pair of candidates where one is preferred to other to pairs array
  • when tied don't add
  • update global pair_count
• Complete the sort_pairs function
  • sort pairs array in decreasing order of strength of victory
  • if equal order doesn't matter
• Complete the lock_pairs function
  • create locked graph
    • add all edges in decreasing order of victory strength so long as the edge would not create a cycle
• Complete the print_winner function
  • print out the name of the candidate who is the source(no arrows lead to it) of the graph

WEEK 4 - Memory

Lab 4

Lab 4: Volume - CS50x 2022

Requirements:

• 3 cmd arguments
  • input - original file
  • output - new file
  • factor - how much original audio should be scaled
• first read and write header to output file
  • number of bytes is defined in HEADER_SIZE
• read rest of data by sample of 2-bytes at a time
  • multiply sample with factor
  • write it to output
• if malloc used
  • must not leak any memory

Problem Set 4

Filter(More)

Requirements

• Implement following functions in helpers.c
  • grayscale
    • should turn image into black and white image
  • reflect
    • should reflect image horizontally
  • blur
    • should turn image into a box-blurred version of the same image
  • edges
    • should highlight edges between objects

Recover

Requirements:

• Implement program recover in file called recover/recover.c
  • Accepts 1 command-line argument
    • name of the image from which to recover JPEGs
    • If one is not provided
      • Remind correct usage
      • Return 1
  • If the image cannot be opened
    • inform the user
    • Return 1
  • Files you generate
    • name pattern: ***.jpg
    • *** - three-digit number 000(zero-padded) - %03i
  • If malloc is used
    • must not leak any memory
  • All opened files should be closed

WEEK 5 - Data structures

Lab 5

Lab 5: Inheritance - CS50x 2022

Requirements

• implement function create_family
  • takes 1 argument
    • int generation
  • should allocate one person for each member of the family of specified number of generations
  • returns pointer to the person in the youngest generation
  • each person should have alleles assigned to them
    • oldest generation randomly chosen
    • younger generation should inherit one allele(random) from each parent
  • each person should have parents assigned to them
    • oldest generation should have both parents set to NULL
    • younger generation should have parents array of two pointers, each pointing to different parent
  • Functionality logic
    • malloc sizeof(person)
    • generations > 1
      • set parent pointers
      • assign alleles
    • generation == 1
      • no parent pointers
      • random alleles
• implement function free_family
  • accept 1 argument
    • pointer to person
  • then free memory for that person
  • then recursively free memory for all their ancestors
    • free both parents before freeing child
    • free child

Problem Set 5

Speller

Speller - CS50x 2022

Requirements:

• Implement load, hash, size, check and unload
  • Effectively as you can use hash table
• Don’t change speller.c or Makefile
• Can alter dictionary.c to complete the implementations
  • Can’t alter declarations
• Check
  • must be case-insensitive
  • return true for words actually in dictionary
  • don’t hardcode common words
  • Possessive is only allowed if it is in dictionary
  • can take only text variable
  • any preprocessed dictionary can’t be saved on disc to improve efficiency
• Assumptions that can be made
  • any dictionary passed will be alphabetically sorted - one word per line, each ending with \n
  • Dictionary contains at least one word
  • Words in dictionary won't exceed the LENGTH constant
  • No word will appear twice
  • Each word will contain lowercase alphabetical characters
  • Possibly apostrophes
  • No word will start with apostrophes
  • Check will be passed only words that correspond to required rules, defined here before - apostrophe, lowercase, uppercase, alphabetical
• Must not leak any memory, use valgrind
• Hash function should be your own, not from online

WEEK 6 - Python

Lab 6

Lab 6: World Cup - CS50x 2022

Requirements:

• Complete the implementation of tournament.py
  • Simulates N number of tournaments and outputs each team’s probability of winning
  • In main function read team data from CSV
    • Add each team to the list teams
    • File will be provided as a command-line argument
    • Access it using sys.arg[1]
    • Use csv.DictReader for reading
    • By default all values read from the file will be strings
    • Append each team to teams dictionary
  • Implement simulate_tournament function
    • should accept single argument teams as input
    • it is list of teams
    • should repeatedly simulate rounds until you're left with one team
    • returns name of the winner
    • you should not assume the number of teams in the tournament, but you may assume it will be a power of 2
  • Implement simulate_tournament in main function
    • run N number of tournament simulations
    • keep track how many times each team wins in the counts dictionary

Problem Set 6

Hello

Hello - CS50x 2022

Requirements:

• write program hello.py that prompts for user's name and prints hello, {name}

Mario (More)

Mario - CS50x 2022

Requirements:

• Write mario.py program
  • recreates half-pyramids using #
  • prompts user with get_int to get half-pyramid height (1-8, inclusive)
    • if user fails to provide positive integer, re-prompt
  • generate desired half-pyramids(height: 4 hashes, width: 4 hashes(for each half-pyramid), gap: 2 spaces)
  • no additional spaces afeter the last set of hashes on each row
  • bottom-left corner aligned with left-hand edge of your terminal window

Credit

Credit - CS50x 2022

Requirements:

• Implement credit.py program
  • prompts user for credit card number
  • prints where it is valid or invalid using Luhn's algorithm and card specific parameters
    • AMEX\n - starts with 34 or 37 and is 15 characters long
    • MASTERCARD\n - starts with 51, 52, 53, 54 or 55 and is 16 characters long
    • VISA\n - starts with 4 and is 13 or 16 characters long
    • INVALID\n
  • you may assume the user's input will be entirely numeric

Readability

Readability - CS50x 2022

Requirements:

• Implement readability.py
  • prompts user to input some text
    • get_string to capture user input
  • outputs the grade level for the text
    • uses Coleman-Liau index to valuate
    • count letters, words and sentences
      • letter is any character from a to z or A to Z
      • character seperated by spaces count as a word
      • occurrence of period, exclamation point, or question mark indicates end of sentence
    • formula: 0.0588 * L - 0.296 * S - 15.8
      • L - average number of letters per 100 words in the text
      • S 0 average number of sentences per 100 words in the text
    • prints value: "Before Grade 1" (<1), "Grade X" (X - rounded to nearest integer 1-16) ,"Grade 16+" (>16)

DNA

DNA - CS50x 2022

Requirements:

• implement dna.py
  • program should require
    • first command-line argument the name of a CSV file containing STR counts for list of individuals
    • second command-line argument the name of a text file containing the DNA sequence to identify
    • if correct number of arguments is provided, you can assume that the files provided are correct (structure, name, type)
  • program should print error
    • when command-line argument count is incorrect
  • program should
    • open CSV and read contents into memory
      • you may assume that the first row of CSV will be the column names
      • first column will be word name and the remaining columns will be the STR sequences themselves
    • open the DNA sequence and read contents into memory
    • compute the longest run of consecutive repeats of the STR in the DNA sequence to identify. Utilize the helper function - longest_match
    • output name of the matching individual when STR counts match exactly
      • you may assume that STR counts will not match more than one individual
    • output No match, when STR do not match exactly with any of the individuals in the CSV file

Week 7 - SQL

Lab 7

Lab 7: Songs - CS50x 2022

Requirements:

• 1.sql - write a SQL query to list the names of all songs in the database
  • Your query should output a table with a single column for the name of each song
• 2.sql - write a SQL query to list the names of all songs in ** increasing order of tempo**
  • Your query should output a table with a single column for the name of each song****
• 3.sql - write a SQL query to list the names of the top 5 longest songs , in descending order of length
  • Your query should output a table with a single column for the name of each song
• 4.sql - write a SQL query that lists the names of any songs that have danceability, energy, and valence greater than 0.75
  • Your query should output a table with a single column for the name of each song
• 5.sql - write a SQL query that returns the average energy of all the songs
  • Your query should output a table with a single column and a single row containing the average energy
• 6.sql - write a SQL query that lists the names of songs that are by Post Malone
  • Your query should output a table with a single column for the name of each song
  • You should not make any assumptions about what Post Malone’s artist_id is
• 7.sql - write a SQL query that returns the average energy of songs that are by Drake
  • Your query should output a table with a single column and a single row containing the average energy
  • You should not make any assumptions about what Drake’s artist_id is
• 8.sql - write a SQL query that lists the names of the songs that feature other artists
  • Songs that feature other artists will include “feat.” in the name of the song
  • Your query should output a table with a single column for the name of each song

Problem set 7

Movies

Movies - CS50x 2022

Requirements:

• In 1.sql, write a SQL query to list the titles of all movies released in 2008.

  • Your query should output a table with a single column for the title of each movie.

• In 2.sql, write a SQL query to determine the birth year of Emma Stone.

  • Your query should output a table with a single column and a single row ( not including the header) containing Emma Stone's birth year.

  • You may assume that there is only one person in the database with the name Emma Stone.

• In 3.sql, write a SQL query to list the titles of all movies with a release date on or after 2018, in alphabetical order.

  • Your query should output a table with a single column for the title of each movie.

  • Movies released in 2018 should be included, as should movies with release dates in the future.

• In 4.sql, write a SQL query to determine the number of movies with an IMDb rating of 10.0.

  • Your query should output a table with a single column and a single row ( not including the header) containing the number of movies with a 10.0 rating.

• In 5.sql, write a SQL query to list the titles and release years of all Harry Potter movies, in chronological order.

  • Your query should output a table with two columns, one for the title of each movie and one for the release year of each movie.

  • You may assume that the title of all Harry Potter movies will begin with the words "Harry Potter", and that if a movie title begins with the words "Harry Potter", it is a Harry Potter movie.

• In 6.sql, write a SQL query to determine the average rating of all movies released in 2012.

  • Your query should output a table with a single column and a single row ( not including the header) containing the average rating.

• In 7.sql, write a SQL query to list all movies released in 2010 and their ratings, in descending order by rating. For movies with the same rating, order them alphabetically by title.

  • Your query should output a table with two columns, one for the title of each movie and one for the rating of each movie.

  • Movies that do not have ratings should not be included in the result.

• In 8.sql, write a SQL query to list the names of all people who starred in Toy Story.

  • Your query should output a table with a single column for the name of each person.

  • You may assume that there is only one movie in the database with the title Toy Story.

• In 9.sql, write a SQL query to list the names of all people who starred in a movie released in 2004, ordered by birth year.

  • Your query should output a table with a single column for the name of each person.

  • People with the same birth year may be listed in any order.

  • No need to worry about people who have no birth year listed, so long as those who do have a birth year are listed in order.

  • If a person appeared in more than one movie in 2004, they should only appear in your results once.

• In 10.sql, write a SQL query to list the names of all people who have directed a movie that received a rating of at least 9.0.

  • Your query should output a table with a single column for the name of each person.

  • If a person directed more than one movie that received a rating of at least 9.0, they should only appear in your results once.

• In 11.sql, write a SQL query to list the titles of the five highest rated movies (in order) that Chadwick Boseman starred in, starting with the highest rated.

  • Your query should output a table with a single column for the title of each movie.

  • You may assume that there is only one person in the database with the name Chadwick Boseman.

• In 12.sql, write a SQL query to list the titles of all movies in which both Johnny Depp and Helena Bonham Carter starred.

  • Your query should output a table with a single column for the title of each movie.

  • You may assume that there is only one person in the database with the name Johnny Depp.

  • You may assume that there is only one person in the database with the name Helena Bonham Carter.

• In 13.sql, write a SQL query to list the names of all people who starred in a movie in which Kevin Bacon also starred.

  • Your query should output a table with a single column for the name of each person.

  • There may be multiple people named Kevin Bacon in the database. Be sure to only select the Kevin Bacon born in 1958.

  • Kevin Bacon himself should not be included in the resulting list.

Fiftyville

Fiftyville - CS50x 2022 SQL style guide indentation

Requirements:

• Solve the mystery using security logs

• Log your SQL queries in log.sql

  • Add labels for queries as a comments:--

  • Explain why you are running that query and what information you are hoping to get

  • You can add additional notes on the thought process

  • Indent your queries, as they may get complex

• Add answers to answers.txt file by filling in the blanks

• Recent theft took place in Humphrey Street, on 28th July

Week 8 - HTML, CSS, JavaScript

Lab 8

Lab 8: Trivia - CS50x 2022

Requirements:

• Part 1
  • use h3 heading for question text
  • button for each possible answer choices
    • at least 3
    • 1 correct
  • add JS logic
    • clicked on incorrect answer, button should turn red and display text beneath the question “Incorrect”
    • clicked on the correct answer, button should turn green and display text beneath the question“Correct!”
• Part 2
  • add part 2 question for text-based answer
    • use h3 heading for question
    • input field for user response
    • button to confirm their answer
  • add JS logic that validates user answer after confirmation
    • the text field should turn red, and display text beneath the question “Incorrect”
    • the text field should turn green and display text beneath the question “Correct!”
• Additionally you can
  • Edit styles.css
  • Add additional trivia questions

Problem set 8

Homepage

Requirements:

• Contain at least four different .html pages
  • one of which is index.html
  • it should be possible to get from any page on your website to any other page by following one or more hyperlinks
• Use at least ten (10) distinct HTML tags besides , , , and <title>
• Integrate one or more features from Bootstrap into your site
  • <link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC" crossorigin="anonymous">
  • <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js" integrity="sha384-MrcW6ZMFYlzcLA8Nl+NtUVF0sA7MsXsP1UyJoMp4YLEuNSfAP+JcXn/tWtIaxVXM" crossorigin="anonymous"></script>
• Have at least one stylesheet file of your own creation, styles.css
  • Which uses at least five different CSS selectors
    • e.g. tag, class or ID
    • within which you use a total of at least five different CSS properties
      • font-size, margin etc
• Integrate one or more features of JavaScript into your site to make your site more interactive.
  • you can use JavaScript to add alerts, to have an effect at a recurring interval, or to add interactivity to buttons, dropdowns, or forms. Feel free to be creative!
• Ensure that your site looks nice on browsers both on mobile devices as well as laptops and desktops.
• Consider also:
  • whether the aesthetics of your site are such that it is intuitive and straightforward for a user to navigate;
  • whether your CSS has been factored out into a separate CSS file(s);
  • whether you have avoided repetition and redundancy by “cascading” style properties from parent tags.

Week 9 - Flask

Lab 8

Lab 9: Birthdays - CS50x 2022

Requirements:

• Route / with GET should display:
  • List of all the people, along with their birthdays in a table
    • In app.py add logic to handle GET request to query birthdays.db for all birthdays. Pass all of that data to your index.html template
    • In index.html add logic to render each birthday.
• Route / with POST should add:
  • New birthday to birthdays.db database and re-render index.html
    • In index.html, add an HTML form. It should let user type in a name, a birthday month, and birthday day.
      • Submit to action /
    • In app.py, add logic to handle for POST request and inserting a new row to birthdays.db
• Optionally:
  • Add ability to delete and/or edit birthdays
  • Additional feature of your choosing

Problem set 9

Finance

C$50 Finance - CS50x 2022

Configuration

1. Visit iexcloud.io/cloud-login#/register/
2. Select the “Individual” account type, then enter your name, email address, and a password, and click “Create account”.
3. Once registered, scroll down to “Get started for free” and click “Select Start plan” to choose the free plan.
4. Once you’ve confirmed your account via a confirmation email, visit Tokens
5. Copy the key that appears under the Token column (it should begin with pk_).
6. In your terminal window, execute:

   $ export API_KEY=value
   

Requirements

• implement register
  • allows a user to register for account via form
  • require username, input name=username
    • render an apology if the user’s input is blank or exists
  • require password, input name=password
  • require same password, input name=confirmation
  • submit via POST to /register
  • insert user into users
    • store hash of user’s password
      • use generate_password_hash
  • create new template for registration
  • give 10000 to user
• implement quote
  • require input stock’s symbol, input name=symbol
  • submit via POST to /quote
  • when users visit /quote via GET
    • render form that submits to /quote via POST
    • then render results from lookup
• implement buy
  • require input stock’s symbol, input name=symbol
    • render an apology if
      • input is blank
      • symbol does not exist lookup
  • require input number of shares, input name=shares
    • render an apology if
      • input is not a positive integer
  • submit via POST to /buy
  • SELECT to find how much cash user has
  • Add one or more tables to finance.db to keep track purchases
    • Use appropriate SQLite types
    • Define UNIQUE indexes on any fields that should be unique
    • Define (non-UNIQUE) indexes on any fields via which you will search
      • (as via SELECT with WHERE)
  • render an apology if
    • user cannot afford the number of shares at the current price.
  • You don’t need to worry about race conditions
• implement index
  • renders table summarizing
    • stocks owned
    • number of shares owned
    • current price
    • total value - shares * price
  • show current cash balance with grand total - stocks total value + cash
  • need to execute multiple SELECTs
• implement sell
  • require input stock’s symbol, input name=symbol
    • render an apology if
      • user fails to select a stock
      • user does not own any shares of that stock
  • require input number of shares, input name=shares
    • render an apology if
      • input is not a positive integer
      • user does not own that many shares of the stock
  • submit via POST to /sell
  • don't need to worry about race conditions
• implement history
  • render table of all transactions - every buy and sell
    • type of transaction
    • stock's symbol
    • price
    • number of shares
    • date and time
    • might alter buy table or create additional table. Minimize redundancies
• personal touch (implement at least one)
  • Allow users to change their passwords
  • Allow users to add additional cash to their account
  • Allow users to buy more shares or sell shares of stocks they already own via index itself, without having to type stock’s symbols manually
  • Require users’ passwords to have some number of letters, numbers, and/or symbols
  • implement some other feature of comparable scope