/// <summary>
/// Privat helper. Breadth First Search from Single Source.
/// </summary>
private void _breadthFirstSearch(IGraph <T> graph, T source)
{
// Define helper variables.
var current = source;
var queue = new DataStructures.Lists.Queue <T>(_verticesCount);
// Set distance to current to zero
_distances[_nodesToIndices[current]] = 0;
// Set current to visited: true.
_visited[_nodesToIndices[current]] = true;
queue.Enqueue(current);
while (!queue.IsEmpty)
{
current = queue.Dequeue();
int indexOfCurrent = _nodesToIndices[current];
foreach (var adjacent in graph.Neighbours(current))
{
int indexOfAdjacent = _nodesToIndices[adjacent];
if (!_visited[indexOfAdjacent])
{
_predecessors[indexOfAdjacent] = indexOfCurrent;
_distances[indexOfAdjacent] = _distances[indexOfCurrent] + 1;
_visited[indexOfAdjacent] = true;
queue.Enqueue(adjacent);
}
} //end-foreach
} //end-while
}
/// <summary>
/// A breadth first search traversal of the graph, starting from a specified vertex.
/// Returns the visited vertices of the graph.
/// </summary>
public virtual IEnumerable <T> BreadthFirstWalk(T source)
{
// Check for existence of source
if (VerticesCount == 0)
{
return(new ArrayList <T>(0));
}
else if (!HasVertex(source))
{
throw new KeyNotFoundException("The source vertex doesn't exist.");
}
var visited = new HashSet <T>();
var queue = new DataStructures.Lists.Queue <T>();
var listOfNodes = new ArrayList <T>(VerticesCount);
listOfNodes.Add(source);
visited.Add(source);
queue.Enqueue(source);
while (!queue.IsEmpty)
{
var current = queue.Dequeue();
var neighbors = Neighbours(current);
foreach (var adjacent in neighbors)
{
if (!visited.Contains(adjacent))
{
listOfNodes.Add(adjacent);
visited.Add(adjacent);
queue.Enqueue(adjacent);
}
}
}
return(listOfNodes);
}
/// <summary>
/// Privat helper. Breadth First Search from Multiple Sources.
/// </summary>
private void _breadthFirstSearch(IGraph <T> graph, IList <T> sources)
{
// Define helper variables.
var queue = new DataStructures.Lists.Queue <T>(_verticesCount);
foreach (var source in sources)
{
if (!graph.HasVertex(source))
{
throw new Exception("Graph doesn't has a vertex '" + source + "'");
}
int index = _nodesToIndices[source];
_distances[index] = 0;
_visited[index] = true;
queue.Enqueue(source);
}
while (!queue.IsEmpty)
{
var current = queue.Dequeue();
int indexOfCurrent = _nodesToIndices[current];
foreach (var adjacent in graph.Neighbours(current))
{
int indexOfAdjacent = _nodesToIndices[adjacent];
if (!_visited[indexOfAdjacent])
{
_predecessors[indexOfAdjacent] = indexOfCurrent;
_distances[indexOfAdjacent] = _distances[indexOfCurrent] + 1;
_visited[indexOfAdjacent] = true;
queue.Enqueue(adjacent);
}
} //end-foreach
} //end-while
}
