how to input this for Dijkstra algorithm question

Question

I have an assignment on Dijkstra's algorithm, but the question has me confused about the input. It asks me to find shortest and second shortest paths, and that part I have figured out, but how do I even start with the graph has me troubled. The question says the input has to be read from a file and the file contains the number of nodes and the weight between two nodes. Weight between two nodes should be 1 to 9, and can use 0 to indicate a path that doesn't exist. Now my question is what has to be the contents of the file? I was able to understand Dijkstra's algorithm where the input was a 2d array that represents the graph. Can someone clarify what is expected from this question? Like what the source file should contain.

I think input format should be defined in the assignment, there are many ways how to represent a graph.. — Ecto
– Ecto, Commented Jun 15, 2020 at 10:52
@Ecto The input is read from a file and contains the number of nodes and the weight between two nodes. Weight between two nodes should be within 1 to 9. You may use 0 to indicate a path that doesn’t exist. This is what the assignment says for input format. That's it. — wakanada
– wakanada, Commented Jun 15, 2020 at 10:54
@wakanada you can represent a weighted Graph as a Matrix, where the entry (i,j) is the weight between Node i and j. When it is an undirected graph it is a symmetrical matrix. If there is no path from i to j use 0. — MGP
– MGP, Commented Jun 15, 2020 at 11:01

Ecto · Accepted Answer · 2020-06-15 11:00:41Z

0

You are probably supposed to create file like this: (example - there are many ways to do it)

4   # number of nodes (from 1 to 4)
1 2 3   # means edge from node 1 to node 2 with weight 3
2 3 1   # means edge from node 2 to node 3 with weight 1
...

this would correspond to 2d matrix like this:

answered Jun 15, 2020 at 11:00

Ecto

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