Project 0x1A.

C - Hash tables

Read or watch:

What is a HashTable Data Structure - Introduction to Hash Tables , Part 0. https://www.youtube.com/watch?v=MfhjkfocRR0
Hash function. https://en.wikipedia.org/wiki/Hash_function
Hash table. https://en.wikipedia.org/wiki/Hash_table
Hash Functions. http://www.cse.yorku.ca/~oz/hash.html

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google.

What is a hash function
What makes a good hash function
What is a hash table, how do they work and how to use them
What is a collision and what are the main ways of dealing with collisions in the context of a hash table
What are the advantages and drawbacks of using hash tables
What are the most common use cases of hash tables

Requirements

General

Allowed editors: vi, vim, emacs
All your files will be compiled on Ubuntu 14.04 LTS
Your programs and functions will be compiled with gcc 4.8.4 using the flags -Wall -Werror -Wextra and -pedantic
All your files should end with a new line
A README.md file, at the root of the folder of the project is mandatory
Your code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl
You are not allowed to use global variables
No more than 5 functions per file
You are allowed to use the C standard library
The prototypes of all your functions should be included in your header file called hash_tables.h
Don’t forget to push your header file
All your header files should be include guarded

Tasks

ht = {} mandatory
djb2 mandatory
key -> index mandatory
ht['betty'] = 'holberton' mandatory
ht['betty'] mandatory
print(ht) mandatory
del ht mandatory
$ht['Betty'] = 'Holberton' #advanced

More Info

Data Structures

Please use these data structures for this project:

/**
 * struct hash_node_s - Node of a hash table
 *
 * @key: The key, string
 * The key is unique in the HashTable
 * @value: The value corresponding to a key
 * @next: A pointer to the next node of the List
 */
typedef struct hash_node_s
{
	 char *key;
	 char *value;
	 struct hash_node_s *next;
} hash_node_t;

/**
 * struct hash_table_s - Hash table data structure
 *
 * @size: The size of the array
 * @array: An array of size @size
 * Each cell of this array is a pointer to the first node of a linked list,
 * because we want our HashTable to use a Chaining collision handling
 */
typedef struct hash_table_s
{
	 unsigned long int size;
	 hash_node_t **array;
} hash_table_t;

Python Dictionaries

Python dictionaries are implemented using hash tables. When you will be done with this project, you will be able to better understand the power and simplicity of Python dictionaries. So much is actually happening when you type d = {'a': 1, 'b': 2}, but everything looks so simple for the user. Python doesn’t use the exact same implementation than the one you will work on today though. If you are curious on how it works under the hood, here is a good blog post about how dictionaries are implemented in Python 2.7 (not mandatory). http://www.laurentluce.com/posts/python-dictionary-implementation/

Note that all dictionaries are not implemented using hash tables and there is a difference between a dictionary and a hash table. Read more here (not mandatory). https://stackoverflow.com/questions/2061222/what-is-the-true-difference-between-a-dictionary-and-a-hash-table

Coding style tests

Holberton Betty style test.

Built With

Emacs editor.
gcc 4.8.4 compiler.
Linux vagrant-ubuntu-trusty-64 3.13.0-170-generic

Author

Leonardo Calderon J. - Initial work - LeoCJJ 01/18/2019

leocjj / sorting_algorithms