CSC152 2006S, Class 30: Notes on Exam 1

Admin:
* Homework: Think about how to implement priority queues.
* Sorry about confusion on Friday's lab.

Overview:
* General notes
* Problem 4: Edit Distance
* Problem 1: Building Fractions
* Problem 2: Comparing Stuff
* Problem 3: Piggy Banks

/General Notes/

* Shortest mostly-correct exam: 4 pages; Longest: 41
* "n.p." means "no penalty"
* Not all of you took advantage of available extra credit.
* Not all of you took advantage of the grade for effort.

* I care about capitalization (but did not take off, this time).
  + Fields, variables, methods: Begin with a lowercase letter.
  + Classes: Begin with uppercase letter, mixed case.
  + Constants: All caps.
  + Packages: All lowercase.
* I care about indentation.
* Extra work can lead to penalties as well as extra credit.
* Don't print error messages in utility classes.

      public void myUtilityMethod()
      {
        PrintWriter pen = new PrintWriter(System.out, true);
        ...
        if (...) {
          pen.println("Sorry, I've noted an error.");
        }
      }

      DO NOT PRINT ERROR MESSAGE IN UTILITY CLASSES
  Programming model

    User
    \O
     |  <-> User Interface <-> Utility methods
    / \

        WHEN THINGS GO WRONG, THROW AN EXCEPTION

/Comparing Strings/

* Some of you made this more difficult than it should have been.
* I tried to give you a straightforward algorithm to translate into code.
* Part of the issue was discovery: How expensive is this algorithm?
  * VERY
  * Gives an edit cost, but at a high cost
  * Does not tell us *how* to edit.

/Fractions/

* Conceptually complicated for some: To build one fraction, you need
  to build others.
  + Possible to do without that conceptual complication, but more
    difficult.
* Some issues with rounding up and rounding down (particularly with
  negative numbers).
  E.g.,
    Fraction smaller = new Fraction((int) Math.round(d), 1);
  Use ceiling and floor.
  

/Comparing Points/

* Most of the necessary utility code was in the reading on classes.
* Many of you got the wrong metric.
* Is it a good metric?  Why or why not?

/Piggybanks/

* Generally fine.