/// <summary>
/// Computes a shortest paths tree from the specified sourceVertex to every other vertex in the edge-weighted directed graph
/// </summary>
/// <param name="graph">The edge-weighted directed graph</param>
/// <param name="sourceVertex">The source vertex to compute the shortest paths tree from</param>
/// <exception cref="ArgumentOutOfRangeException">Throws an ArgumentOutOfRangeException if an edge weight is negative</exception>
/// <exception cref="ArgumentNullException">Thrown if EdgeWeightedDigraph is null</exception>
public DijkstraShortestPath(EdgeWeightedDigraph graph, int sourceVertex)
{
if (graph == null)
{
throw new ArgumentNullException("graph", "EdgeWeightedDigraph cannot be null");
}
foreach (DirectedEdge edge in graph.Edges())
{
if (edge.Weight < 0)
{
throw new ArgumentOutOfRangeException($"Edge: '{edge}' has negative weight");
}
}
_distanceTo = new double[graph.NumberOfVertices];
_edgeTo = new DirectedEdge[graph.NumberOfVertices];
for (int v = 0; v < graph.NumberOfVertices; v++)
{
_distanceTo[v] = double.PositiveInfinity;
}
_distanceTo[sourceVertex] = 0.0;
_priorityQueue = new IndexMinPriorityQueue <double>(graph.NumberOfVertices);
_priorityQueue.Insert(sourceVertex, _distanceTo[sourceVertex]);
while (!_priorityQueue.IsEmpty())
{
int v = _priorityQueue.DeleteMin();
foreach (DirectedEdge edge in graph.Adjacent(v))
{
Relax(edge);
}
}
}
/// <summary>
/// Computes a shortest paths tree from the specified sourceVertex to every other vertex in the edge-weighted directed graph
/// </summary>
/// <param name="graph">The edge-weighted directed graph</param>
/// <param name="sourceVertex">The source vertex to compute the shortest paths tree from</param>
/// <exception cref="ArgumentOutOfRangeException">Throws an ArgumentOutOfRangeException if an edge weight is negative</exception>
/// <exception cref="ArgumentNullException">Thrown if EdgeWeightedDigraph is null</exception>
public DijkstraShortestPath( EdgeWeightedDigraph graph, int sourceVertex )
{
if ( graph == null )
{
throw new ArgumentNullException( "graph", "EdgeWeightedDigraph cannot be null" );
}
foreach ( DirectedEdge edge in graph.Edges() )
{
if ( edge.Weight < 0 )
{
throw new ArgumentOutOfRangeException( string.Format( "Edge: '{0}' has negative weight", edge ) );
}
}
_distanceTo = new double[graph.NumberOfVertices];
_edgeTo = new DirectedEdge[graph.NumberOfVertices];
for ( int v = 0; v < graph.NumberOfVertices; v++ )
{
_distanceTo[v] = Double.PositiveInfinity;
}
_distanceTo[sourceVertex] = 0.0;
_priorityQueue = new IndexMinPriorityQueue<double>( graph.NumberOfVertices );
_priorityQueue.Insert( sourceVertex, _distanceTo[sourceVertex] );
while ( !_priorityQueue.IsEmpty() )
{
int v = _priorityQueue.DeleteMin();
foreach ( DirectedEdge edge in graph.Adjacent( v ) )
{
Relax( edge );
}
}
}
private void Prim(EdgeWeightedGraph G, int s)
{
_distTo[s] = 0.0;
_pq.Insert(s, _distTo[s]);
while (!_pq.IsEmpty())
{
int v = _pq.DeleteMin();
Scan(G, v);
}
}
List <List <int> > GetMST()
{
var size = nodes.NodeList.Count;
var parents = new int[size];
var weights = new float[size];
var marked = new bool[size];
var pq = new IndexMinPriorityQueue <float>(size);
for (var x = 1; x < size; x++)
{
weights[x] = float.MaxValue;
}
weights[0] = 0;
pq.Insert(0, 0);
while (!pq.IsEmpty())
{
int v = pq.DeleteMin();
marked[v] = true;
for (var x = 0; x < size; x++)
{
if (x != v && !marked[x])
{
var distance = Vector2.Distance(nodes.NodeList[v], nodes.NodeList[x]);
if (distance < weights[x])
{
weights[x] = distance;
parents[x] = v;
if (pq.Contains(x))
{
pq.ChangeKey(x, distance);
}
else
{
pq.Insert(x, distance);
}
}
}
}
}
var result = GetAdjacencyLists(size);
for (var x = 1; x < parents.Length; x++)
{
var target = parents[x];
result[x].Add(target);
result[target].Add(x);
}
return(result);
}
public PrimMinimumSpanTree(EdgeWeightedGraph g)
{
edgeTo = new Edge[g.Vcount];
distTo = new double[g.Vcount];
marked = new bool[g.Vcount];
for (int i = 0; i < g.Vcount; i++)
{
distTo[i] = double.PositiveInfinity;
}
pq = new IndexMinPriorityQueue <double>(g.Vcount);
distTo[0] = 0.0;
pq.Insert(0, 0.0);
while (!pq.IsEmpty())
{
Visit(g, pq.DelMin());
}
}
public DijkstraShortestPath(EdgeWeightedDigraph g, int s)
{
edgeTo = new DirectedEdge[g.Vcount];
distTo = new double[g.Vcount];
pq = new IndexMinPriorityQueue <double>(g.Vcount);
for (int i = 0; i < g.Vcount; i++)
{
distTo[i] = double.PositiveInfinity;
}
distTo[0] = 0.0;
pq.Insert(s, 0.0);
while (!pq.IsEmpty())
{
Relax(g, pq.DelMin());
}
}
public void IsEmpty_AfterConstructingNewQueue_WillBeTrue()
{
IndexMinPriorityQueue <double> queue = new IndexMinPriorityQueue <double>(10);
Assert.IsTrue(queue.IsEmpty());
}