CSC153 2004S, Class 48: Priority Queues

Admin
* Lots to cover today; avoid distractions
* Class may be cancelled on Wednesday; Homework still due
* Questions on HW7?
  * Why a circularly-linked doubly-linked list?  Because you learn by building one.
  * How do I write all of the stuff to a file?
    * Method one:
      * Write a toString method for tasks
      * Write a constructor for tasks that takes a string as a parameter
      * The rest is obvious
    * Method two: Serialize
      * Make your class implement Serializable
      * Write using an ObjectOutputStream (built from a FileOutputStream)
      * Read using an ObjectInputStream (built from a FileInputStream)
      * See Person.java, CerealOut.java, CerealIn.java
      * You can probably make TaskList (and everything else) serializable and all will be hunkydory.
  * How does writeObject work?  Sam's guess
    * First, verify that the object is serialable
    * Next, determine the fields of the object (using getClass and getFields)
    * Write the type of the object
    * For each field, get the value and write it to the file
    * When you have an object field, write a "placeholder" and put the object on a queue (or stack) of other objects that must be written
    * Recursively write anything in the queue/stack
  * How does readObject work?  Sam's guess
    * The opposite
  * What are the odds we'll get a test or some homework back?  100%
  * What are the odds it will be graded when we get it back? 100%
  * What are the odds it will be before the end of the semester? 100%
  * What are the odds it will be Wednesday? 25%

Overview:
* Priority queue basics
* Simple implementations
* Detour: Binary trees
* Heaps
* An alternate implementation of heaps