//Here there one additional array "distTo" which tells you how many edges there is to "v" vertex from starting "s" vertex.
//I use Adjacency List Graph so if you want to test code provided below or solve some problems you can use this Graph :
public BreadthFirstSearch(GraphAdjList G, int s)
{
edgeTo = new int[G.VertexCount];
distTo = new int[G.VertexCount];
for (int i = 0; i < G.VertexCount; i++)
{
distTo[i] = -1;
edgeTo[i] = -1;
}
this.s = s;
BFSearch(G, s);
}
static void Main(string[] args)
{
GraphAdjList g = new GraphAdjList(4);
g.AddEdge(0, 1);
g.AddEdge(0, 2);
g.AddEdge(1, 2);
g.AddEdge(2, 0);
g.AddEdge(2, 3);
g.AddEdge(3, 3);
BreadthFirstSearch bfs = new BreadthFirstSearch(g, 2);
}
public void BFSearch(GraphAdjList G, int S)
{
var queue = new Queue <int>();
queue.Enqueue(S);
distTo[S] = 0;
while (queue.Count != 0)
{
int v = queue.Dequeue();
Console.Write(v + " ");
foreach (var w in G.GetAdj(v))
{
if (distTo[w] == -1)
{
queue.Enqueue(w);
distTo[w] = distTo[v] + 1;
edgeTo[w] = v;
}
}
}
}
