CS2 Winter 2005

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CS2 Winter 2005

• Elementary Algorithms
• and Data Structures

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• Course objectives, (from CS2 web site)
• Algorithhm Complexity, limits of computation.
• Software Design, modularization and abstraction.
• Data Structures - Gain familiarity with basic
  data structures
• Object Oriented Programming -
• Algorithm Strategies - divide-and-conquer, greedy
  algorithms, dynamic-programming, etc
• Formal Reasoning - correctness of an algorithm or
  program.
• Numerics tform continuous math concepts into
  discrete programs.
• Today bullet 3 More on Data structures,
  recursion, etc.

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Taxonomy of Elementary Data structures

• Array
• A set of items which are randomly accessible by
  numeric index.
• Quick insertion, fast access if indices are known
• Disadvantages Slow search, slow deletion, costly
  to change size
• Stack
• A collection of items where only the most
  recently added item may be removed.
• The latest added item is at the top.
• Basic operations are push and pop.
• Often top and isEmpty are available, too.
• Also known as "last-in, first-out" or LIFO
  because it provides last-in, first out access
• Disadvantages Slow access to other items
• Queue
• Provides first-in, first out access
• Disadvantages Slow access to other items
• List
• A collection of items accessible one after
  another beginning at the head and ending at the
  tail.

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• Binary tree, other trees
• Quick search, insertion, deletion, (if tree
  remains balanced)
• Disadvantages Deletion algorithm is complex
• Graphs
• Models of real-world connections
• Disadvantages Some algorithms are slow and
  complex

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• Linked list
• Quick insertion, quick deletion
• Disadvantages slow search
• Hash Table
• Very fast access if key is known. Fast insertion
• Disadvantages Slow deletion, access slow if key
  is not known.
• Heap
• Fast insertion, deletion, access to largest item
• Disadvantages slow access to other items

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Arrays

• A0..99 data array, indexed by integers
• AI,J 2D data array, indexed by 2 integers,
  etc.