JiwoonKim / CS50-Pset-General-Programming

Problem set solutions to Harvard's CS50 lectures

CS50 Psets: Computer Science and General Programming

Solutions implemented for CS50x from 2016 to 2018.

Problem Sets (Psets): Pset 1 to Pset 5.

Couldn't find the files for previous Pset solutions (the less comfortable versions from pset1 to pset3) I had implemented in C, so saving the solutions for the more comfortable versions implemented in Python for pset6 sentimentals part instead.

For following Psets: Solutions for Pset 6 to Pset 8

💡 Pset1: hello, mario, cash, credit

Initially solved hello, mario(less comfortable version), cash(the less comfortable version) in C language in January, 2016.

Solved hello, mario(more comfortable version), cash(the more comfortable version) in Python language in June, 2018.

• hello: a simple program printing "hello" on the screen.

  first program in C, getting to know how to compile(using the make utility configured by CS50) and execute a .c file.

• mario: a program that prints out a full-pyramid of a specified height given by user.

  • the less comfortable version: print out a half-pyramid.

  learned how to use conditions and loops. helped get familiar with using standard I/O (using CS50's training wheels: get_int()).

• cash: a program that calculates the minimum number of coins required to give a user change.

  learned how to implement a Greedy algorithm and how to handle the inherent imprecision of floating-point values.

• credit: a program that determines whether a provided credit card number is valid according to Luhn’s algorithm (If valid, print the which company it belongs to:American Express, MasterCard, or Visa).

  learned how to use various math functions and operators to interact with numeral values.

💡 Pset2: caesar, vigenère, crack

Initially, solved caesar(the less comfortable version), vigeniere(the less comfortable version) in C language in January, 2016.

Solved crack(the more comfortable version) in Python in June, 2018.

• caesar: a program that encrypts messages using Caesar’s cipher.

• vigenère: a program that encrypts messages using Vigenère’s cipher.

• crack: a program that cracks passwords encryped by C's DES-based crypt function (hash function).

learned about encryption and decryption, hash funcitons, ASCII values, how to use command-line arguments in programs, manipulate strings, and convert chars to integers.

💡 Pset3: fifteen

Initially, Pset3 was to implement a game of fifteen in February, 2016.

Unfortunately, could not find source code I implemented.

💡 Pset4: whodunit, resize, recover

Solved whodunit, resize(more comfortable version), recover in C language in February, 2016 and in July, 2018.

• whodunit: a program that reveals a hidden message in a BMP by removing the red noise in it.

  learned how an Image file is constructed by bits, specifically how a BMP file is formatted in hexadecimals to represent RGB in pixels.

  Also learned how to use header files, structs, and got familiar with using file I/O.

• resize: a program that resizes (shrinks or enlarges) BMPs by a factor of f given by the user.

  learned how to dynamically allocate memory using malloc and use valgrind to debug and check memory leaks.

• recover: a program that recovers JPEGs from a forensic image (.raw file).

  learned how a JPEG file is formatted and about the FAT file system and blocks.

💡 Pset5: speller

Solved speller in C language in July, 2018.

• dictionary: a program that contains the functions for loading a dictionary from disk to memory, spell-checking each word in a file based on the dictionary, counting the total number of words in the dictionary, and finally unloading the dynamically allocated dictionary from memory.

  • implemented functions check, load, size, unload in dictionary.c to be used in speller.c.

  learned how to create a functions for a header file (c file -> h file), how to use pointers

  Also learned how to implement Data structures, specifically a trie for constructing a dictionary dynamically in the memory.