1. fundamentals of algorithms

• algorithm

  a set of instructions that instruct a computer system
• a good algorithm will have pre-conditions which illustrate what resources are required to perform the instructions, in terms of processing power or additional files
• flowchart symbols

  A) start/stop

  B) input/output

  C) subroutine

  D) process

  E) decision

  F) connector

  
• pseudocode

  a simple way of describing a set of instructions in a manner that resembles a programming language
• decomposition

  breaking a problem down into smaller tasks
• abstraction

  the process of filtering out the characteristics of problems that are not needed in order to concentrate on those that are needed
• data structures are used in programming to store data - there are two main types:

  • arrays
  • record
• arrays:

  • consist of a single row containing integers, just like a single row of a table
  • use place value in terms of naming each value in the list (this is called indexing)
  • the first integer in the array is 'index 0', the second integer is 'index 1', etc.
• record:

  • contains fields to stor data in, in the same way as a database
  • groups together related data fields
  • in python, dictionaries are used as records
• sort algorithm

  used to sort data in an array in ascending or descending order
• search algorithms

  used to retrieve data based on search criteria
• linear simply means working through a sequence in order, so therefore the linear search algorithm will search for an integer by comparing the search integer to each integer in an array
• the binary search algorithm can only be used with sorted arrays
• binary search algorithm works by:

  • starting at the middle integer and initially identifying whether this matches the criteria
  • in many cases it wont , and if this is the case the algorithm will continue
  • next the program will workout whether the values in the array are sorted in ascending (smallest to largest) or descending (largest to smallest) order
  • it will then disregard the half which will not contain the criteria
  • the algorithm will then identify the matching criteria, at this point it is quicker than the linear search algorithm as the integers in the array are ordered
• bubble sort algorithm

  works by comparing each integer in the list, or 'array', to the next integer in the list, working from left to right
• the merge sort algorithm works in a similar way to the bubble sort algorithm, except in a more efficient way as the ‘problem’ is broken down into smaller ‘problems'