** Graphs**

A * graph* *G = (V, E)* has a set of * vertices*
or * nodes* *V* and a set of * edges*
or * arcs* or * links* *E*,
where each edge connects two vertices. We write this
mathematically as *E ⊆ V X V*, where *X* is called
the * Cartesian product* of two sets.
We can write an edge as a
pair *(v _{1}, v_{2})*, where

A * path* is a sequence of vertexes connected by edges:
*v _{1}, v_{2}, ..., v_{n}* where

An edge may have a * weight* or * cost* associated with it.