Data Structures & Algorithms Notes Page

What’s Hashing?

Definition:

• It’s a way to store and find data quickly using a special method called a hash function!
• Kinda like assigning every item a “locker number” based on its name

Hash Functions:

• A hash function takes a key (like a word or number) and turns it into a number called a hash code
  • This number decides where to store this data

Simple Visual Example (Concept Only):

int hashCode = key.hashCode();  // Java does this under the hood

The HashMap

Definition:

• A HashMap stores key-value pairs
• Each key is unique and is mapped to exactly one value

Example:

• Kind of like a dictionary:
  • Key: cat
  • Value: small animal