Essential things to remember from today's class (class 7, 13th September)

How to save and restore a binary tree, preserving its exact shape.

What a Priority Queue as an abstract data type is.

Various possible implementations of a PQ, and their pros and cons.

What exactly a Min-Heap is, the rules it must obey to be valid.

How and why you would store a min heap in a vector (or possibly array).

How to efficiently perform the two major min-heap operations,
   inserting a new item with its associated priority, and
   removing the item with the lowest priority.