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using System.Text.RegularExpressions;
using Graph.Interfaces;
namespace Graph.IO
{
public static class GraphFile
{
// read a graph from file using IFileReader (i.e. Dependancy injection for unit testing)
public static Graph<double> Read(IFileReader reader)
{
string[] lines = reader.Lines;
Graph<double> graph = new Graph<double>();
foreach (string line in reader.Lines)
{
// split string into vertex id and the edges
string[] parts = line.Split(" ", 2);
// parse vertex id
int vertex = int.Parse(parts[0]);
// parse edges, matches pairs of number two at a time, i.e. "num num"
Match match = Regex.Match(parts[1], @"[^ ]+ [^ ]+");
while (match.Success)
{
// for each match, split the "vertex weight" pair
string[] edge = match.Value.Split(" ", 2);
// add edge to graph (vertex1, vertex2, weight)
graph.AddEdge(new Edge<double>(
vertex,
int.Parse(edge[0]),
double.Parse(edge[1])
));
// iterate match
match = match.NextMatch();
}
}
return graph;
}
// write a graph to file using IFileWriter (i.e. Dependancy injection for unit testing)
public static void Print(Graph<double> graph, IFileWriter writer)
{
// create array of strings with a size equal to vertices
string[] lines = new string[graph.Vertices.Count];
// add each vertex to it's parents output line
graph.Vertices.ForEach(vertex =>
{
// do nothing if it has no parent
if (vertex.Parent == null)
return;
// needed due to making vertex.Parent nullable
int parent = vertex.Parent.GetValueOrDefault();
// for vertex & parent, create string if not already
lines[vertex.Id] ??= $"{vertex.Id}";
lines[parent] ??= $"{parent}";
// add vertex + weight to parent's string & visa versa
lines[parent] += $" {vertex.Id} {vertex.Key.ToString("F1")}";
lines[vertex.Id] += $" {parent} {vertex.Key.ToString("F1")}";
});
// write the array of strings to file
writer.WriteAllLines(lines);
}
}
}
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