CS 211 Data Structures and Algorithms Lab

Examination

Objective To implement Dijkstra’s algorithm to find the shortest

path distances from a source vertex to every vertex

Total marks 15

Penalty for violating naming

convention(s)

5%

The objective of this assignment is to implement Dijkstra’s algorithm to find the shortest path distances

from a source vertex to every vertex in the input graph, which is directed and has non-negative weights

on edges.

Inputs

Your program should accept two command-line arguments: an input file and the label of a source vertex.

A typical execution of your program will be ./a.out sample.graph 14.

[Note#1: 14 represents the source vertex]

[Note#2: The provided sample output files such as: dijkstra.txt, dijkstra1.txt and dijkstra2.txt,

corresponds to source vertex 14, 442 and 75, respectively.]

[Note#3: The source to source should be printed zero. This can be verified in the provided output files]

The input file represents a directed graph with non-negative integer weights on edges. Every node in the

graph is uniquely labelled with a non-negative integer. Every line in the input file is of the form x y w ,

which represents a directed edge from node x to node y , where the weight of the edge is w . No edge

is repeated in the input file. The second command-line argument is the label of a source vertex, which is

guaranteed to be a vertex in the given graph.

Task

Implement Dijkstra’s algorithm to find the shortest path distances from the given source vertex to all

vertices in the given graph. It is recommended that you use min-priority queue with the binary min-heap

implementation, but a simpler implementation is also accepted with full credits.

Output

Your program should create a file named ‘dijkstra.txt’. Every line in the output file should corresponds to

a shortest path distance from source to a vertex and should be of the form:

<target> <shortest-path-distance-from-source>

Example: If there is a line “47 1452” in the output file and 14 is the source vertex, then it implies that the

shortest path distance from 14 to 47 is 1452. If there is no path from the source to a vertex, say 21, then

the corresponding output line must be “21 -1”.

Shortest path distances of vertices from the source can be printed in the output file in any order.

Submission and Evaluation

Please note that there is no second evaluation for the examination.

● The program you submit should output ‘dijkstra.txt’ when run.

● The main file of your program should be named as <roll no>.<extension>, where roll no. specifies

your roll no. and the extension depends on the language you choose (Usage of C is mandatory

for this assignment). Ex: 200010001.c.

● Test well before submission. You may use the attached sample input file(s) for testing. The

corresponding output file(s) is also attached. Please note that this is only for reference – an error

in these files is not a valid reason for an error in your program! We have some hidden inputs

with us to test your program. The mark you obtain is purely based on whether your program

correctly gives outputs for the hidden inputs.

● If your program has only a single source file, please submit the file as it is. If your program has

multiple source files, please submit your code as a zip file where the name of the zip file should

be your roll number. It is important that you follow the input/output conventions exactly

(including the naming scheme) as we may be doing an automated evaluation. There will be a

penalty of 5% (on the mark you deserve otherwise) if you do not follow the naming

conventions exactly.

● Follow some coding style uniformly. Provide proper comments in your code.

● Submit only through moodle. Submit well in advance. Any hiccups in the moodle/internet at the

last minute is never acceptable as an excuse for late submission. Submissions through email or

any other means will be ignored.

● Acknowledge the people (other than the instructor and TA) who helped you to solve this

assignment. The details of the help you received and the names of the people who helped you

(including internet sources, if applicable) should come in the beginning of the main file as a

comment. Copying others’ programs and allowing others to copy your program are serious

offences and a deserving penalty will be imposed if found.

● The marks you obtain will be proportional to the number of correct vertex-distance pairs in the

output file.