public void TestAlgorthim()
{
MemoizationTable memoTable = new MemoizationTable();
Vertex initialVertex = new Vertex();
Vertex secondaryVertex = new Vertex();
Vertex tertiaryVertex = new Vertex();
Vertex quaternaryVertex = new Vertex();
initialVertex.AddEdgeTowardsOtherVertex(secondaryVertex, 3);
initialVertex.AddEdgeTowardsOtherVertex(tertiaryVertex, 15);
secondaryVertex.AddEdgeTowardsOtherVertex(tertiaryVertex, 7);
secondaryVertex.AddEdgeTowardsOtherVertex(quaternaryVertex, 4);
tertiaryVertex.AddEdgeTowardsOtherVertex(initialVertex, 1);
tertiaryVertex.AddEdgeTowardsOtherVertex(secondaryVertex, 1);
tertiaryVertex.AddEdgeTowardsOtherVertex(tertiaryVertex, 1);
tertiaryVertex.AddEdgeTowardsOtherVertex(quaternaryVertex, 1);
memoTable.AddVertex(initialVertex);
memoTable.AddVertex(secondaryVertex);
memoTable.AddVertex(tertiaryVertex);
memoTable.AddVertex(quaternaryVertex);
memoTable.CalculateShortestPath(initialVertex);
Assert.Equal(0, memoTable.ShortestPathsTable.FirstOrDefault(x => x.Vertex == initialVertex).LowestCostPath);
Assert.Equal(3, memoTable.ShortestPathsTable.FirstOrDefault(x => x.Vertex == secondaryVertex).LowestCostPath);
Assert.Equal(10, memoTable.ShortestPathsTable.FirstOrDefault(x => x.Vertex == tertiaryVertex).LowestCostPath);
Assert.Equal(7, memoTable.ShortestPathsTable.FirstOrDefault(x => x.Vertex == quaternaryVertex).LowestCostPath);
}
/// <summary>
/// Extension method to calculate shortest paths using Dijkstra's Algorithm.
/// </summary>
/// <param name="memoTable">Memoization Table</param>
/// <param name="vertex">Vertex To calculate path from</param>
/// <returns>Updated memoization table</returns>
public static MemoizationTable CalculateShortestPath(this MemoizationTable memoTable, Vertex vertex)
{
memoTable.Update(vertex, 0);
int costToCurrentVertex = 0;
// TODO: swap out infinite loop
while (true)
{
// initialise edge
Edge smallestEdgeToUnvisitedVertex = null;
// Find lowest weighted edge to an unvisited vertex from current vertex
bool changed = false;
foreach (Edge edge in vertex.GetDirectedEdges().Where(x => !x.DirectedTo.Visited))
{
memoTable.Update(edge.DirectedTo, costToCurrentVertex + edge.Weight);
if ((smallestEdgeToUnvisitedVertex == null) || (edge.Weight < smallestEdgeToUnvisitedVertex.Weight))
{
smallestEdgeToUnvisitedVertex = edge;
changed = true;
}
}
if (changed == false)
{
// All vertices visited
break;
}
// Visit nearest unvisited vertex with smallest cost
vertex = smallestEdgeToUnvisitedVertex.DirectedTo;
costToCurrentVertex += smallestEdgeToUnvisitedVertex.Weight;
}
return(memoTable);
}