/// <summary>
/// Find the shortest path to the target vertex
/// </summary>
/// <param name="graph"></param>
/// <param name="from"> initial vertex </param>
/// <param name="to"> target vertex </param>
/// <typeparam name="T"></typeparam>
/// <returns> vertex and path to it </returns>
public Tuple <T, IEnumerable <T> > ShortestPath <T>(Graph <T> graph, T from, T to)
{
var previous = new Dictionary <T, T>();
var queue = new Queue <T>();
queue.Enqueue(from);
while (queue.Count > 0)
{
var vertex = queue.Dequeue();
foreach (var neighbor in graph.GetNeighbors(vertex))
{
if (!previous.TryAdd(neighbor, vertex))
{
continue;
}
queue.Enqueue(neighbor);
}
}
var path = new List <T>();
var current = to;
while (!current.Equals(from))
{
path.Add(current);
current = previous[current];
}
path.Add(from);
path.Reverse();
return(new Tuple <T, IEnumerable <T> >(from, path));
}
/// <summary>
///
/// </summary>
/// <param name="graph"></param>
/// <param name="start"> starting vortex</param>
/// <typeparam name="T"></typeparam>
/// <returns> visited vertices </returns>
public HashSet <T> VisitAll <T>(Graph <T> graph, T start)
{
var visited = new HashSet <T>();
if (!graph.ContainsVertex(start))
{
return(visited);
}
var queue = new Queue <T>();
queue.Enqueue(start);
while (queue.Count > 0)
{
var vertex = queue.Dequeue();
// continue if exists or add
if (!visited.Add(vertex))
{
continue;
}
foreach (var neighbor in graph.GetNeighbors(vertex))
{
if (!visited.Contains(neighbor))
{
queue.Enqueue(neighbor);
}
}
}
return(visited);
}
