Problem Solving

• This is section 1.1 of your book.
• So we have decided that
  • Computer science involves problem solving.
  • You really should read the first paragraph of this section
    • CS is problem solving
    • But so is everything else.
    • So perhaps CS is using computers to solve problems
• There is no single problem solving strategy or technique.
• George Polya, wrote a book called How To Solve It which has some great suggestions.
  • Google has a Copy
• Polya suggests a general approach:
  1. Understand the problem
     • What are we asked to do?
     • What is the input?
     • What is the output?
     • What do I and don't I know.
  2. Devise a plan
     • This is the meat and potatoes of the book.
     • He mentions many different approaches.
     • This focuses on math problems, but we will look at it quickly
  3. Carry out the plan
     • This includes checking at each step for correctness
  4. Evaluate the solution
     • Can you check to see if it is correct
     • Can you show it is correct.
• We will be back to Polya later.
• Our author suggests that the problem solving in cs follows
  1. Design
  2. Implementation
  3. Testing
  4. Refinement.
• There is a long standing, (bad) method of software development called the Waterfall Method that follows these steps
  1. Develop the Software
  2. Develop a plan to solve the problem
     • This is sometimes called an algorithm
  3. Test the algorithm
  4. Translate the algorithm into code
  5. Test the code
  6. Use/maintain/fix the code
• 
• At EVERY point you should test your solution.
• At any point you may need to go back to a previous point.
• We will investigate all of these stages in more depth later.
• There are two basic design strategies
  • Top down design:
    • Or functional decomposition
    • Break the big problem into smaller and smaller parts
    • Until the parts become easy to manage
  • Bottom up design:
    • What little pieces do I need to solve a problem?
    • Build these and combine them to form a solution.