C-Trains Programming Problem

The examples from this README are encoded into the tests. In order to run the tests, you must have Python 3 and pytest. You can install pytest with:

pip install pytest

and run from this directory (i.e. the one containing this README) with:

py.test -v

Otherwise, any Python 3 interpreter should be able to use graph.py to build a graph and compute the various properties related to the problem below.

Background

Calgary is expanding its train service with one-way routes between various stations. This program is intended to provide customers with information about the routes, including:

• the distance along certain routes
• the number of different routes between two stations
• the shortest route between two stations

Suppose our routes were as follows:

Departing Station	Arrival Station	Distance (km)
A	B	5
B	C	4
C	D	8
D	C	8
D	E	6
A	D	5
C	E	2
E	B	3
A	E	7

The program must be able to compute the following:

1. The distance along the route A-B-C (9)
2. The distance along the route A-D (5)
3. The distance along the route A-D-C (13)
4. The distance along the route A-E-B-C-D (22)
5. The distance along the route A-E-D (no such route)
6. The number of routes starting at C and ending at C with at most 3 stops (2)
7. The number of routes starting at A and ending at C with exactly 4 stops (3)
8. The distance along the shortest route from A to C (9)
9. The distance along the shortest route from B to B (9)
10. The number of different routes from C to C with a distance of less than 30 (7)

(For the "number of routes" and "shortest routes" examples, ignore the 0-length routes!)