Description
Q1: Adjacency (25 points)
You will read a directed graph from a text file. Below is an example, found in Graph1.txt:
5
1 2 0.2 4 10.1 5 0.5
2 1 1.5
3 2 100.0 4 50.2
4
5 2 10.5 3 13.9
The first line is the number of vertices. Each vertex is represented by an integer from 1 to N. Each line
is of the form:
…
For each vertex, you have a list of the adjacent vertices with positive edge weights. For instance, in
the above example, vertex 1 is connected to vertex 2 (edge weight 0.2), to vertex 4 (edge weight 10.1)
and to vertex 5 (edge weight 0.5). Vertex 2 is connected to vertex 1 (edge weight 1.5), vertex 4 has no
outgoing edges, etc.
Represent the graph using an adjacency list. Create your graph class inside graph.h
In order to test your implementation, you will read a second text file (let us call it
AdjacencyQueries1.txt) that will contain a set of pair of vertices.
Your program (name it
CreateGraphAndTest.cc) will have to first create the graph by reading it from the text file
Graph1.txt. It will then open the file AdjacencyQueries1.txt and for each pair of vertices in it, your
program will print whether the vertices are adjacent or not, and if they are, your program will print the
weight of the edge that connects them.
For example, if the file AdjancencyQueries1.txt contains:
4 1
3 4
1 5
5 1
1 3
Then the output should be:
4 1: not_connected
3 4: connected 50.2
1 5: connected 0.5
5 1: not_connected
1 3: not_connected
where the numbers to the right of “connected” are the weight of this edge.
Note: This example is consistent with Graph1.txt. It is very important that you follow this format
exactly. Make sure you have the “_” underscore in “not_connected”. Make sure there is nothing extra
printed.
So, your program can be called for example as:
./CreateGraphAndTest
Exact deliverables are described at the bottom of the file.
Q2: Dijkstra’s Algorithm Implementation (60 points)
Using your graph implementation in Q1, implement Dijkstra’s Algorithm using a priority queue (i.e.
heap). Write a program that runs as follows:
./FindPaths
This program should use Dijkstra’s Algorithm to find the shortest paths from a given starting vertex to
all vertices in the graph file.
The priority queue data structure is provided for you under the file, binary_heap.h, and included
inside graph.h. Do not modify binary_heap.h, we will use the original automatically.
You should then print out the paths to every destination. For example, if you run the program having
as input Graph2.txt (provided) starting from vertex 1, i.e.
./FindPaths Graph2.txt 1
Then the output should be:
1: 1 cost: 0.0
2: 1 2 cost: 2.0
3: 1 4 3 cost: 3.0
4: 1 cost: 1.0
5: 1 4 5 cost: 3.0
6: 1 4 7 6 cost: 6.0
7: 1 4 7 cost: 5.0
The first number is the target vertex. (Aka: the last line beginning with 7: is the shortest path from the
input starting vertex 1, to the target vertex 7.) Your output should always be ordered this way,
starting from target vertex 1, to the maximum target vertex for that graph.
Following the target vertex, display the path taken, inclusive of the starting and ending vertices.
Finally, display “cost: ” followed by the cost of that path.
Special Case: Unreachable Vertices
There is a special case that may arise based on the input graph and the starting vertex. This is the case
when there is no path from a starting vertex to the destination. In such cases, you should include the
word not_possible in your output. This case arises multiple times in the following:
./FindPaths Graph2.txt 7
Then, the output should be:
1: not_possible
2: not_possible
3: not_possible
4: not_possible
5: not_possible
6: 7 6 cost: 1.0
7: 7 cost: 0.0
The above means that there are no paths starting from vertex to vertices 1,2,3,4, and 5. Thus, when
there is no path to a target vertex, add the word not_possible to your output.
Note: This an example using the inputs provided in Graph2.txt. It is very important that you follow the
output format exactly. Do not print any extra lines or characters.
Deliverables: You should submit these files: **MAKE SURE TO SUBMIT ALL RELEVANT
FILES. CHECK YOUR INCLUDE STATEMENTS. DO NOT PRINT ANYTHING OTHER
THAN WHAT IS ASKED**
● README file (for all questions as described in class)
Q1
● CreateGraphAndTest.cc
o graphTestDriver() – All functionality should be in here, NOT the main.
● graph.h
o Use this for the relevant graph class and its routines.
Q2
● FindPaths.cc
o pathfindDriver() – All functionality should be in here, NOT the main.
● graph.h
o Use this for the relevant graph class and its routines. Modify with the relevant
functions needed by pathfindDriver().
Do not submit or modify binary_heap.h and dsexceptions.h. The originals will be
included automatically when you submit.
CSCI 335 HW 5
