// TODO: What happens if two nodes are at the same "lowest cost"?
private string FindLowestCostNodeId(FastestPathTable fastestPathTable, HashSet <string> visitedNodeIds)
{
int lowestCost = int.MaxValue;
string lowestCostNodeId = null;
foreach (var row in fastestPathTable.Rows)
{
if (!visitedNodeIds.Contains(row.NodeId) && row.LowestCost < lowestCost)
{
lowestCost = row.LowestCost;
lowestCostNodeId = row.NodeId;
}
}
return(lowestCostNodeId);
}
public void ShouldGenerateValidTable_WhenGivenUnconnectedGraphNodes()
{
// Arrange
var nodes = GenerateUndirectedGraphNodes();
nodes.Add(new Node {
Id = "F", Neighbors = null
});
var expectedResult = new FastestPathTable()
{
PrimaryNodeId = "A",
Rows = new List <FastestPathRow>
{
new FastestPathRow {
NodeId = "A", LowestCost = 0, NeighborNodeId = null
},
new FastestPathRow {
NodeId = "B", LowestCost = 3, NeighborNodeId = "D"
},
new FastestPathRow {
NodeId = "C", LowestCost = 7, NeighborNodeId = "E"
},
new FastestPathRow {
NodeId = "D", LowestCost = 1, NeighborNodeId = "A"
},
new FastestPathRow {
NodeId = "E", LowestCost = 2, NeighborNodeId = "D"
},
new FastestPathRow {
NodeId = "F", LowestCost = int.MaxValue, NeighborNodeId = null
}
}
};
var dijkstraService = CreateService();
var request = new FindShortestPathsRequest {
Nodes = nodes, PrimaryNodeId = "A"
};
// Act
var results = dijkstraService.FindShortestPaths(request);
// Assert
results.Should().BeEquivalentTo(expectedResult);
}
private FastestPathTable CreateFastestPathTable(List <Node> nodes, string primaryNodeId)
{
var fastestPathTable = new FastestPathTable();
foreach (var node in nodes)
{
fastestPathTable.Rows.Add(new FastestPathRow
{
NodeId = node.Id,
LowestCost = node.Id == primaryNodeId ? 0 : int.MaxValue,
NeighborNodeId = null
});
}
fastestPathTable.PrimaryNodeId = primaryNodeId;
return(fastestPathTable);
}
public void ShouldGenerateValidTable_WhenGivenDirectedGraphNodes()
{
// Arrange
var nodes = GenerateUndirectedGraphNodes();
// Remove the neighbor E from node D to make it directed (D->E)...
var nodeDNeighbors = nodes.FirstOrDefault(n => n.Id == "D").Neighbors;
nodeDNeighbors.RemoveAll(n => n.NodeId == "E");
var expectedResult = new FastestPathTable()
{
PrimaryNodeId = "A",
Rows = new List <FastestPathRow>
{
new FastestPathRow {
NodeId = "A", LowestCost = 0, NeighborNodeId = null
},
new FastestPathRow {
NodeId = "B", LowestCost = 3, NeighborNodeId = "D"
},
new FastestPathRow {
NodeId = "C", LowestCost = 8, NeighborNodeId = "B"
},
new FastestPathRow {
NodeId = "D", LowestCost = 1, NeighborNodeId = "A"
},
new FastestPathRow {
NodeId = "E", LowestCost = 5, NeighborNodeId = "B"
}
}
};
var dijkstraService = CreateService();
var request = new FindShortestPathsRequest {
Nodes = nodes, PrimaryNodeId = "A"
};
// Act
var results = dijkstraService.FindShortestPaths(request);
// Assert
results.Should().BeEquivalentTo(expectedResult);
}
private List <string> FindPath(FastestPathTable table, string startNodeId, string endNodeId)
{
var path = new List <string> {
startNodeId
};
var rowsByNodeId = table.Rows.ToDictionary(r => r.NodeId);
var currentNodeId = startNodeId;
while (currentNodeId != endNodeId && currentNodeId != null)
{
currentNodeId = rowsByNodeId[currentNodeId].NeighborNodeId;
path.Add(currentNodeId);
}
if (currentNodeId == null)
{
path = null;
}
return(path);
}
