changed default parent value from null to -1

2 files changed, 5 insertions, 8 deletions

diff --git a/IO/GraphFile.cs b/IO/GraphFile.cs
index 4d12f34..42a1b2b 100644
--- a/IO/GraphFile.cs
+++ b/IO/GraphFile.cs
@@ -51,19 +51,16 @@ namespace Graph.IO
             graph.Vertices.ForEach(vertex =>
             {
                 // do nothing if it has no parent
-                if (vertex.Parent == null)
+                if (vertex.Parent == -1)
                     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}";
+                lines[vertex.Parent] ??= $"{vertex.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")}";
+                lines[vertex.Parent] += $" {vertex.Id} {vertex.Key.ToString("F1")}";
+                lines[vertex.Id] += $" {vertex.Parent} {vertex.Key.ToString("F1")}";
             });
             // write the array of strings to file
             writer.WriteAllLines(lines);
diff --git a/Vertex.cs b/Vertex.cs
index 814bea6..628b552 100644
--- a/Vertex.cs
+++ b/Vertex.cs
@@ -10,7 +10,7 @@ namespace Graph
         public int Id { get; set; }
         public T Key { get; set; }
 
-        public int? Parent { get; set; } = null;
+        public int Parent { get; set; } = -1;
         public List<Edge<T>> Edges { get; set; } = new List<Edge<T>>();
 
         // indexer for accessing edge with v of index