start implementing graph immutability

Author: matiii

src/Dijkstra.NET/ShortestPath/ImmutableDijkstra.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using Dijkstra.NET.Contract;
+using Dijkstra.NET.Extensions;
+using Dijkstra.NET.Model;
+using Dijkstra.NET.Utility;
+
+namespace Dijkstra.NET.ShortestPath
+{
+    public class ImmutableDijkstra<T, TEdgeCustom> : Dijkstra<T, TEdgeCustom> where TEdgeCustom : IEquatable<TEdgeCustom>
+    {
+        public ImmutableDijkstra(IGraph<T, TEdgeCustom> graph) : base(graph)
+        {
+        }
+
+        public override IShortestPathResult Process(uint @from, uint to)
+        {
+            var result = new DijkstraResult(from, to);
+            Graph[from].Distance = 0;
+            var q = new SortedSet<INode<T, TEdgeCustom>>(new[] { Graph[from] }, new NodeComparer<T, TEdgeCustom>());
+            var current = new HashSet<uint>();
+
+            while (q.Count > 0)
+            {
+                INode<T, TEdgeCustom> u = q.Deque();
+                current.Remove(u.Key);
+
+                if (u.Key == to)
+                {
+                    result.Distance = u.Distance;
+                    break;
+                }
+
+                for (int i = 0; i < u.Children.Count; i++)
+                {
+                    Edge<T, TEdgeCustom> e = u.Children[i];
+
+                    if (e.Node.Distance > u.Distance + e.Cost)
+                    {
+                        if (current.Contains(e.Node.Key))
+                            q.Remove(e.Node);
+
+                        e.Node.Distance = u.Distance + e.Cost;
+                        q.Add(e.Node);
+                        current.Add(e.Node.Key);
+                        result.Path[e.Node.Key] = u.Key;
+                    }
+                }
+            }
+
+            return result;
+        }
+    }
+}

src/Dijkstra.NET/ShortestPath/Model/ShortPathJob.cs

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+namespace Dijkstra.NET.ShortestPath.Model
+{
+    public struct ShortPathJob
+    {
+        public uint NodeKey { get; set; }
+
+        public int Distance { get; set; }
+
+    }
+}