Dictionaries, Maps, Skip List

Map

ADT that stores key-value pairs

You give it a key, and it returns the associated object/value.
Each key is unique (no duplicates).
Example: Think of it like a real dictionary — the word is the key, and the definition is the value.

A Dictioary is a generalisation of a Map

In a Map, each key can only have one associated object.
In a Dictionary, a key can have many objects (one-to-many relationship).

Ex:

(5, "A")
(7, "C")
(7, "D")

Maps are used for look-up tables, where you quickly find a single value for a key:
- System properties (like configuration values)
- Compiler symbol tables (variables and their memory addresses)
Dictionaries are used when multiple items share the same key:
- Log files (many logs under the same category)
- Query results from a database (e.g. multiple rows matching one search condition)

Method	What it does
`isEmpty()`	returns `true` if the map has no entries
`size()`	returns how many key–value pairs exist
`insertItem(Key k, Object o)`	adds a new pair (key, value)
`removeElement(Key k)`	deletes the pair for that key
`findElement(Key k)`	returns the value associated with `k`, or `null` if not found
`containsKey(Key k)`	checks if a key exists
`containsValue(Object o)`	checks if a value exists