Overview of the different algorithm topic categories

The following algorithm topic categories are currently supported and filled with at least some content in the ANIMAL AV system. Please note that some of the categories may only provide examples for a certain combination of natural and programming language!

  • Backtracking algorithms try out one possible solution for a problem until they have either solved the problem or found a "dead end". In the latter case, they go backwards one step ("backtrack") and take the next possible route - again, until the problem has been solved or a "dead end" has been encountered. A "dead end" is typically an illegal state, the meaning of which depends on the underlying problem. For example, in the "8 Queens Problem", eight queens have be placed on a chessboard so that no queen may strike another queen. Here, an illegal state occurs whenever one queen can strike another one (note: this will always be due to the last queen placed). In other applications, a state may be "illegal" if its result is already worse than the best result found so far.
  • Compression algorithms describe how content can be stored using less space than if it were stored directly - and of course how the original content can be restored from the "space-shrunk version". Typical and popular examples include space-saving storage of images (for example, using the JPG or PNG format instead of the bitmap-based BMP format), audio (MP3 versus WAV), video (MP4 and other formats), as well as the compression of large archives (ZIP being probably the most well-known format) - which are also typically used when you download Windows, Linux, or Mac OS X installation files.
  • Cryptography algorithms deal with making content "unreadable", or at least harder to read, for unintended parties - and how to restore the actual content by the intended recipient. As such, they are widely used in communication, for example in the https:// protocol that indicates an encrypted data transmission between your browser and the server, and should be used whenever privileged data such as passwords or bank account-related information is transferred.
    ANIMAL is - together with its cryptographic visualisations for Caesar, Vigenere, Nihilist and DES - part of the wide-spread, open-source e-learning program CrypTool v1 (http://www.cryptool.org).
  • Data structures algorithms portray the characteristic behaviour of a given data structure, for example how data is inserted, found, or deleted.
  • Graph algorithms include many algorithms in Computer Science that deal for example with finding the cheapest route from one node to another. They are used in many concrete problems, so that a good understanding of graph algorithms is very important for a good programmer.
  • Graphics algorithms deal with approaches to render objects on the screen, or determine which objects shall be shown in which order and to what degree. For example, if a 5000x3000 pixels large image shall be shown on a far smaller area, it either has to be scaled "appropriately" to fit the area available to it, or it should be "cropped": those portions of the image not visualizable on the output area do not have to be drawn, saving computation effort.
  • Hardware-based algorithms visualize the behaviour of the hardware components underlying modern computers, for example logic gates or multiplexers.
  • Hashing algorithms allow the representation of arbitrary content linked to a "key". For example, the complete data of a student may be retrieving by providing the student's student ID as the "key". If used properly, hashing allows "instanteous" access, avoiding the effort to search for the data in a collection, such as a list or array.
  • Mathematics also contains a set of algorithms, although mathematicians would typically not label them in that way. This includes various approaches to determine eigenvalues, invert matrices, or (cleverly) multiply matrices.
  • Misc is the "catch-all" category for all algorithms that do not fall into any of the other categories.
  • Networking algorithms portray Internet protocols and their data flow or show how the (typically graph-based) routing algorithms that determine how to send data from client A to client B work.
  • Searching algorithms deal with finding a given element in a collection. Apart from well-known algorithms such as Binary Searching, this also includes other applications, such as finding a text inside a larger text - a typical application for any text editor (but harder to implement well than one might at first think!).
  • Sorting algorithms work on reordering a collection of elements into a well-defined order. The order can be rather straightforward (e.g., ascending numbers), but can also be more elaborate (e.g., phone books order persons by family name, followed by first name, street and then phone number if the previous entries were identical).
  • Tree algorithms work on another very important data structure used in many algorithms. They can be used for easy and efficient navigation among elements, and to represent hierarchical structures, among (many) other applications.

As you can see, there is a lot to explore using ANIMAL!

© Dr. Guido Rößling 1998-today