#HashFunctions

[joelekm]

Cryptography and Blockchain

Cryptography plays a fundamental role in the world of blockchain technology. It ensures the security and integrity of transactions within a blockchain network by encrypting data and providing authentication mechanisms. Public and private keys, a cornerstone of cryptography, enable users to securely interact with the blockchain, sign transactions, and access their digital assets. Hash functions, another critical component, create unique fingerprints for data blocks, ensuring their immutability and consistency. As blockchain continues to evolve and find applications beyond cryptocurrencies, cryptography remains at the forefront, safeguarding the decentralized and trustless nature of this revolutionary technology.

[normally0]

"Exploring the Many Meanings of 'Hash Room'"

The term "hash room" at Charterhouse School refers to a classroom, but the word "hash" can have several other interpretations:

1. **Hash (Culinary)**: A dish consisting of chopped meat, potatoes, and sometimes other vegetables, often cooked together.

2. **Hash (Computing)**: A function that converts input data of various lengths into a fixed-size string of text, used in various computer science applications like data retrieval and encryption.

3. **Hash (Symbol)**: The symbol "#" which is commonly used in social media as a "hashtag" or in telephone keypads as the "pound" sign.

4. **Hash (Slang for Marijuana)**: Short for hashish, which is a concentrated form of cannabis made from the resin of the cannabis plant.

5. **Hash (Mix-Up)**: To make a mess of or to jumble up something.

Given these different interpretations, "hash room" could be seen as an informal or whimsical term, with the specific meaning tied closely to the unique vernacular of Charterhouse School, where it specifically means a classroom.

#CharterhouseSlang #HashRoom #BoardingSchoolLife #SchoolTraditions #HashRecipe #FoodLovers #HashFunction #CodingLife #Hashish #CannabisCulture #HashItOut #MessySituations #Hashtag #SocialMedia #Trending

[x-pedda]

Programming Tip of the Day

Since perfect hashfunctions don't exist, never use a map, don't worry modern CPUs are fast. O(n²) isn't that slow on an i9.

[veuhoffblog]

Was ist Hashing und wie wird ein Hashwert berechnet?

Der Begriff Hashing beschreibt ein Verfahren, bei dem eine große Anzahl von Datenmengen in kleinere, eindeutige Zeichenfolgen umgewandelt werden. Die umgewandelten Zeichenfolgen werden nach der Verarbeitung als Hashwert oder Hashcode bezeichnet.

In der IT sind Begrifflichkeiten wie Hashing, Hashfunktion und Hashwert längst keine Seltenheit mehr. In diesem Beitrag versuche ich euch verständlich zu erklären, wie die Berechnung eines Hashwertes funktioniert und welche Vorteile uns der Hash-Algorithmus bringt...[Weiterlesen]

[felord]

CSCI203/803 Exercise 5 – Hashing Solved

This exercise is to be completed during your week 8 laboratory class. When you complete the exercise show your work to your lab tutor to have your work marked. The marking is based mainly on correct implementation and code readability. You should implement your code in one file (e.g. ex5.cpp, ex5.c, ex5.java). Make sure your program has a header comment block accontaining the name of the exercise, your name and your student login (e.g. jfk01). You may implement your solution in C, C++, Java or Python.   For this exercise, you are to implement a simple hash table. Your program should prompt for the name of an input file and the read and process the data contained in the file.   The file contains a sequence of integer values. Read them and construct a hash table using chaining. For this exercise, you should use linked lists implemented with dynamic data, as shown below

  Your program should read each integer in turn and calculate its hash value using mod 100 as the hashing function. Thus, if the key is k, the hash value h(k) = k mod 100.   When you have finished calculate and print: The number of empty entries in the hash table. The length of the longest chain.   As usual, do not use STL or equivalent. Page 2 has pseudo code of some algorithms you might use.   When you are finished, test your program using the provided text file named “ex5.txt” and show your code and the output to your lab tutor to receive your mark. Also, submit your file via unix (banshee) using the submit command below.  

$ submit -u login -c CSCI203 –a ex5 filename

  where ‘login' is your UNIX login ID and ‘filename’ is the name of your file.   If you are unable to attend your lab class and demonstrate your work on time due to circumstances beyond your control (e.g. sickness), contact your lecturer  to request an extension.   1    

Pseudo Code

    insert( int key, int value )      create newNode, assign value to it,     set newNode.next to null    if hashTable is NULL then         hashTable = newNode    else         Node^ currentNode = hashTable         while currentNode.next != NULL             currentNode = currentNode.next         end while         currentNode.next = newNode    end if  end insert()     int hashFunction( int value )         calculate hashKey from value     return hashKey   end hashFunction()     main()     try to open input file,   print error & exit if file not found  

      initise hash table

      while file has more data...             get hash key from hash function         insert value into hashTable at key         end while       print nubmer of empty entries and collisions        

end main()

  2   Read the full article

[weusegadgets]

MIT's Introduction to Algorithms, Lectures 7 and 8: Hashing https://t.co/j7HyEBiomq #symboltable #doublehashing #algorithms #dictionary #insert #chaining #hash #hashfunction #perfecthashing #divisionmethod #linearprobing #openaddressing #hashtable #delete #multiplicationmethod

[bubbly-studies]

The task this week is to complete the pseudo code for the following hash table

The task this week is to complete the pseudo code for the following hash table operations:

Insert Remove Assume Hashtable is a simple array of size 8, with indices 0..7. Numeric keys are mapped by a Hashfunction that gives the mod(8,n) value for any key “n” yielding the Hashtable index for that key (0..7). A Hashtable entry is null unless a key exists with that index as its hashed index; if so,…

[braverph]

The task this week is to complete the pseudo code for the following hash table

The task this week is to complete the pseudo code for the following hash table operations:

Insert Remove Assume Hashtable is a simple array of size 8, with indices 0..7. Numeric keys are mapped by a Hashfunction that gives the mod(8,n) value for any key “n” yielding the Hashtable index for that key (0..7). A Hashtable entry is null unless a key exists with that index as its hashed index; if so,…

[zeereblogs]

The task this week is to complete the pseudo code for the following hash table

The task this week is to complete the pseudo code for the following hash table operations:

Insert Remove Assume Hashtable is a simple array of size 8, with indices 0..7. Numeric keys are mapped by a Hashfunction that gives the mod(8,n) value for any key “n” yielding the Hashtable index for that key (0..7). A Hashtable entry is null unless a key exists with that index as its hashed index; if so,…

[ibsurvival]

The task this week is to complete the pseudo code for the following hash table

The task this week is to complete the pseudo code for the following hash table operations:

Insert Remove Assume Hashtable is a simple array of size 8, with indices 0..7. Numeric keys are mapped by a Hashfunction that gives the mod(8,n) value for any key “n” yielding the Hashtable index for that key (0..7). A Hashtable entry is null unless a key exists with that index as its hashed index; if so,…

[deltainfoteklive]

How to Implement HashMap in Java from Scratch

Implementing a HashMap from scratch in Java may seem like a daunting task, but understanding the underlying concepts and following a step-by-step guide can simplify the process. In this article, we will explore the implementation of a HashMap, its benefits, and the various considerations to keep in mind. HashMap is a data structure in Java that stores key-value pairs. It is part of the java.util package and provides an efficient way to retrieve, update, and delete values based on their corresponding keys. The HashMap class in Java provides methods for adding, retrieving, and removing key-value pairs, making it a versatile data structure for various applications. Understanding the concept of key-value pairs In HashMap, each key is associated with a value. These key-value pairs are stored internally using an array of linked lists. The key is used to determine the index of the array where the value is stored. This associative mapping allows for quick retrieval of values based on their keys. Benefits of using HashMap in Java There are several benefits to using HashMaps in Java: - Fast retrieval: HashMap provides constant-time performance for retrieving values based on their keys, making it suitable for scenarios where fast access to data is required. - Flexibility: HashMap can store different data types as values, making it a versatile choice for various applications. - Efficient memory utilization: HashMap dynamically resizes itself depending on the number of elements it contains, optimizing memory usage. - Easy to use: The HashMap class in Java provides easy-to-use methods for adding, retrieving, and removing key-value pairs, simplifying the development process. A step-by-step guide to implementing HashMap from scratch Creating a HashFunction class To implement a HashMap, we first need to create a HashFunction class. This class will be responsible for generating an index based on the key. The HashFunction should distribute the keys uniformly across the array to minimize collisions. Creating a Node class Next, we create a Node class that represents each element in the HashMap. Each Node will contain a key-value pair and a reference to the next Node in case of collisions. Implementing the put() method The put() method is used to add key-value pairs to the HashMap. Inside this method, we calculate the index using the HashFunction, create a new Node, and insert it at the appropriate position. If a collision occurs, we handle it using chaining, where we append the new Node to the existing linked list at that index. Implementing the get() method The get() method is used to retrieve a value based on a given key. Inside this method, we calculate the index using the HashFunction and traverse the linked list at that index looking for a matching key. If found, we return the corresponding value; otherwise, we return null. Handling collisions using chaining Chaining is a technique used to handle collisions in HashMap. When multiple keys hash to the same index, we store them in a linked list at that index. This allows us to store and retrieve multiple values associated with the same index. Exploring the time complexity of HashMap operations The time complexity of various HashMap operations is as follows: - Insertion (put): O(1) average case, O(n) worst case (when there are many collisions) - Retrieval (get): O(1) average case, O(n) worst case (when there are many collisions) - Deletion (remove): O(1) average case, O(n) worst case (when there are many collisions) Efficiency considerations and best practices To ensure optimal performance when using HashMap, consider the following best practices: - Choosing a suitable initial capacity: Set the initial capacity of the HashMap based on the estimated number of key-value pairs. This prevents frequent resizing, improving performance. - Avoiding excessive load factor: The load factor determines when the HashMap should resize itself. Setting a lower load factor increases memory efficiency but may result in more collisions. - Using immutable keys: Immutable keys help maintain the integrity of the HashMap and prevent unexpected behavior. - Properly override hashCode() and equals(): If custom objects are used as keys, make sure to correctly override the hashCode() and equals() methods for proper functioning of the HashMap. Conclusion Implementing a HashMap from scratch in Java provides a deeper understanding of how this data structure works. By following the step-by-step guide, you can create a functional HashMap that efficiently stores and retrieves key-value pairs. Remember to consider efficiency considerations and best practices to optimize the performance of your HashMap implementation. FAQs: What is the difference between HashMap and HashTable? HashMap and HashTable are both data structures in Java that store key-value pairs. However, there are a few differences between them. - HashMap is not synchronized, making it more efficient for single-threaded applications. HashTable, on the other hand, is synchronized and can be used in multi-threaded environments. - HashMap allows null values and a single null key, whereas HashTable does not accept null keys or values. - HashMap is generally preferred over HashTable due to its better performance and flexibility. How does HashMap handle null keys and values? In HashMap, null values can be stored and retrieved like any other value. However, only a single null key can be stored in a HashMap. When a null key is inserted, the index is calculated as 0, and any subsequent null key is also stored at the same index. Retrieving a null key returns the corresponding value stored at index 0. Can we have duplicate keys in a HashMap? No, HashMap does not allow duplicate keys. If a duplicate key is added to the HashMap, the existing value associated with that key will be overwritten by the new value. Is HashMap thread-safe? No, HashMap is not thread-safe. If multiple threads access a HashMap concurrently and perform modifications, it can lead to unexpected results or a concurrent modification exception. To achieve thread-safety, you can use ConcurrentHashMap or synchronize the access to the HashMap externally. Can we iterate over the elements of a HashMap? Yes, you can iterate over the elements of a HashMap using a loop and the appropriate iterator. You can obtain the set of key-value pairs using the entrySet() method and then iterate through them using a for-each loop or an iterator. This allows you to perform operations on each key-value pair in the HashMap. Read the full article

[conflictcfinterest]

The task this week is to complete the pseudo code for the following hash table

The task this week is to complete the pseudo code for the following hash table operations:

Insert Remove Assume Hashtable is a simple array of size 8, with indices 0..7. Numeric keys are mapped by a Hashfunction that gives the mod(8,n) value for any key “n” yielding the Hashtable index for that key (0..7). A Hashtable entry is null unless a key exists with that index as its hashed index; if so,…

[patheticappblr]

The task this week is to complete the pseudo code for the following hash table

The task this week is to complete the pseudo code for the following hash table operations:

Insert Remove Assume Hashtable is a simple array of size 8, with indices 0..7. Numeric keys are mapped by a Hashfunction that gives the mod(8,n) value for any key “n” yielding the Hashtable index for that key (0..7). A Hashtable entry is null unless a key exists with that index as its hashed index; if so,…

[chicken-fuelled-inspiration]

The task this week is to complete the pseudo code for the following hash table

The task this week is to complete the pseudo code for the following hash table operations:

Insert Remove Assume Hashtable is a simple array of size 8, with indices 0..7. Numeric keys are mapped by a Hashfunction that gives the mod(8,n) value for any key “n” yielding the Hashtable index for that key (0..7). A Hashtable entry is null unless a key exists with that index as its hashed index; if so,…

[felord]

CCC ArrayDictionary Solved

Remove from ArrayDictionary The ArrayDictionary class implements the Dictionary interface as a dictionary with chaining capability for key collision. The hash function of this class is: private int hashFunction(String key) { // not ideal return key. length(); As stated in the comment, this is not the most capable solution for a hash function but it helps us test the knowledge Of the hash key…