Question

I am trying to parse a text file that is of the form:

A B 2  
A G 6   
A C 99  
...  
B C 7  
B E 2  
B G 99

Now, these represent “nodes” and the “costs” between them to implement a shortest path algorithm.
I have decided to create a Node class that has 2 instance variables, a name and an array of hashes that are the neighboring nodes and costs to get there.

I am trying to figure out how to parse the file into a series of node objects from each group of lines.
The cost of 99 mean the nodes aren’t connected.

Answer 1

First of all, you should also have a Graph class to manage the nodes and edges. Then something like this should get you started:

g = Graph.new
File.open('your_data_file').each do |line|
    n1, n2, wt = line.split(/\s+/)
    n1 = g.find_or_create_node(n1)
    n2 = g.find_or_create_node(n2)
    wt = wt.to_i
    g.add_edge(n1, n2, wt) if(wt != 99)
end
# g is now your fully populated graph.

The graph, g, tracks the nodes it has so find_or_create_node can return the node if it already exists or create it and cache it if not. The add_edge method would connect n1 and n2 with an edge of weight wt.to_i.

Your shortest path algorithm would, presumably, be a method call on the graph objects.