Algorithms

Algorithms

1. Computational Thinking

   • Decomposition
     • breaking a complex problem down into smaller problems and solving each one individually
   • Algorithmic Thinking
     • a logical way of getting from the problem to the solution. If the steps you take to solve a problem follow an algorithm then they can be reused and adapted to solve similar problems in the future.
   • Abstraction
     • picking out the important bits of information from the problem, ignoring the specific details that don't matter

2. Pseudocode

   • is not actual programming language but it should follow a similar structure and read like one (roughly)
   • clearly shows an algorithm's steps without worrying about the finer details (syntax) of any particular programming language
   • it is quick to write and can be easily converted into any programming language
   • different ways to write pseudocode they are all equally correct as long as the person reading it can follow it and understand what you mean

3. Flow Diagrams

   • Start/Stop
     • the beginning and the end of the algorithm are put in boxes with rounded corners
   • Inputs/Outputs
     • anything that's put into or taken out of the algorithm goes in a parallelogram box
   • Processes
     • general instructions, processes and calculation go in rectangular boxes
   • Decision
     • decision, often a 'yes' or 'no' question, are put in diamond boxes
   • Sub-Routine
     • sub-routines are like sub programs-they reference other flow diagrams
   • Arrows
     • arrows connect boxes and show the direction you should follow. Some boxes might have multiple arrows coming in or going out of them

4. Binary Search

   • 1
     • find the middle item in the ordered list
   • 2
     • if this is the item you're looking for, then stop the search - you've found it
   • 3
     • if not, compare the item you're looking for to the middle item. If it comes before the middle item, get rid of the second half of the list. If it comes after the middle item, get rid of the first half of the list.
   • 4
     • you'll be left with a list that is half the size of the original list. Repeat steps 1-3 on this smaller list to get an even smaller one. Keep going until you find the item you're looking for.

5. Linear Search

   • 1
     • look at the first item in the unordered list.
   • 2
     • if this is the item you're looking for, then stop the search - you.ve found it