Version 2.0
The Programming of week 01 has already completed.
Individual work.
Need to add comment in the programming assignment.

Notice :
	When constructing the adjacancy list, adding the edge separately to incoming vertex and outcoming vertex.
        e.g : [(1,2,-900)], adding (1,2,-900) to vetex 1 and adding (2,1,-900) to vertex 2.

modified:   03.primAssignment.py