Representing a graph from an adjacency list

It may be more convenient to construct a graph given an adjacency list. In this recipe, we will use the built-in package Data.Graph to read a mapping of a vertex to a list of connected vertices.

Getting ready

We will be constructing the graph represented in the following diagram:

How to do it...

Create a new file, which we will name Main.hs, and insert the following code:

1. Import the Data.Graph package:

   import Data.Graph

2. Use the graphFromEdges' function to obtain a tuple that contains the graph. A graph data structure, Graph, is in the first element of the tuple returned. The second element of the tuple contains mappings from a vertex number to its corresponding value, Vertex -> (node, key, [key]):

   myGraph :: Graph
   
   myGraph = fst $ graphFromEdges'   [ ("Node 1", 1, [3, 4] )
                                     , ("Node 2", 2, [3, 4]) 
                                     , ("Node 3", 3, [4])
                                     , ("Node 4", 4, []) ]

3. Print out...