/// <summary>
/// check that algorithm computes either the topological order or finds a directed cycle
/// </summary>
/// <param name="G"></param>
/// <param name="v"></param>
private void dfs(Digraph G, int v)
{
onStack[v] = true;
marked[v] = true;
foreach (int w in G.Adj(v))
{
//short circuit if directed cycle found
if (cycle != null)
{
return;
}
else if (!marked[w])
{
edgeTo[w] = v;
dfs(G, w);
}
//trace back directed cycle
else if (onStack[w])
{
cycle = new Stack <int>();
for (int x = v; x != w; x = edgeTo[x])
{
cycle.Push(x);
}
cycle.Push(w);
cycle.Push(v);
}
}
onStack[v] = false;
}
/// <summary>
/// bfs from single source
/// </summary>
/// <param name="g"></param>
/// <param name="s"></param>
private void bfs(Digraph g, int s)
{
Queue <int> q = new Queue <int>();
for (int i = 0; i < g.V; i++)
{
distTo[i] = INFINITY;
}
//we can reach s
distTo[s] = 0;
marked[s] = true;
q.Enqueue(s);
while (q.Count > 0)
{
int v = q.Dequeue();
foreach (int w in g.Adj(v))
{
if (!marked[w])
{
edgeTo[w] = v;
distTo[w] = distTo[v] + 1;
marked[w] = true;
q.Enqueue(w);
}
}
}
}
/// <summary>
/// bfs from multi sources
/// </summary>
/// <param name="g"></param>
/// <param name="sources"></param>
private void bfs(Digraph g, IEnumerable <int> sources)
{
Queue <int> q = new Queue <int>();
foreach (int s in sources)
{
marked[s] = true;
distTo[s] = 0;
q.Enqueue(s);
}
while (q.Count > 0)
{
int v = q.Dequeue();
foreach (int w in g.Adj(v))
{
if (!marked[w])
{
edgeTo[w] = v;
distTo[w] = distTo[v] + 1;
marked[w] = true;
q.Enqueue(w);
}
}
}
}
private void dfs(Digraph g, int v)
{
marked[v] = true;
foreach (int w in g.Adj(v))
{
if (!marked[w])
{
dfs(g, w);
}
}
}
/// <summary>
/// depth first search
/// </summary>
/// <param name="g"></param>
/// <param name="v"></param>
private void dfs(Digraph g, int v)
{
//before this run, marked[v] always false
marked[v] = true;
count++;
connected.Add(v);
foreach (int w in g.Adj(v))
{
if (!marked[w])
{
edgeTo[w] = v;
dfs(g, w);
}
}
}
/// <summary>
/// run DFS in digraph G from vertex v and compute preorder/postorder
/// </summary>
/// <param name="g"></param>
/// <param name="v"></param>
private void dfs(Digraph g, int v)
{
if (marked[v])
{
return;
}
marked[v] = true;
pre[v] = preCounter++;
preorder.Enqueue(v);
foreach (int w in g.Adj(v))
{
if (!marked[v])
{
dfs(g, w);
}
}
postorder.Enqueue(v);
post[v] = postCounter++;
}