CS 226
Homework 9
Due Monday April 30, 9 a.m.

R-13.6 (please write out the DAG for this list of courses)

R-13.8

R-13.14

R-13.18 (please write out the graph for this question)

Programming:

Implement a system for finding the shortest path in a graph.  The
graph will be specified using an input file. For example the file:

Node Baltimore
Node Philly
Node NewYork
Node Boston
Node Pittsburgh
Edge Baltimore Pittsburgh 260
Edge Baltimore Philly 90
Edge Philly NewYork 120
Edge NewYork Boston 200
Edge Boston Pittsburgh 300

Would specify a graph with 5 nodes and 5 edges. Each edge connects two
nodes as specified and carries a numeric label.  You may assume that:

1) All nodes will be defined before any edges are defined.
2) All nodes have string labels with no spaces.
3) All edges carry non-negative integer weights.
4) All input will be correct (that is, you are not required to find
errors in the input file, although you may want to do this, anyway).

Your program should read the graph from the file graphspec.txt, and
then prompt for a starting point and destination, i.e. input/output
for the graph above would be:

Starting point: Baltimore
Destination: Boston

Path = Baltimore to Philly to NewYork to Boston

Distance = 410

It is up to you to choose a graph representation and to implement an
algorithm for shortest path. You may use any of the code appearing in
the book WEB site or create you own.