Essential algorithms for GCSE and A Level Computer Science

Fundamental data structures

A feature of imperative programming languages, these abstractions of memory allow for the creation of higher order data structures.

What is a dictionary?

A dictionary is a data structure used for storing related data.  It is often referred to as an associative array, as it stores two sets of data that are associated with each

other by mapping keys to values. It is also known as a key-value pair or hashmap.  A dictionary is an implementation of a hash table search but is usually a fundamental data type in high-level languages.  

Instead of a programmer having to code a hash table search, high-level languages provide the dictionary data type within the language. The single value in a key-value pair can also be a list of items, making this a very versatile data structure for a programmer.

Dictionary videos

What extra is in the book?

This algorithm / data structure has its own dedicated chapter in the book, which includes:

  1. Overview
  2. Typical applications / uses
  3. Typical operations
  4. The algorithm written out in simple-structured English
  5. The algorithm written out in pseudocode
  6. Full code listing Python
  7. Full code listing in Visual Basic
  8. Diagrammatic walk-through
  9. Efficiency discussion with reference to Big-O notation

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