public DFSDiagraph(Digraph graph)
{
marked = new bool[graph.V];
order = new Stack<int>(graph.V);
for (int v = 0; v < graph.V; v++)
if (!marked[v]) dfs(graph, v);
}
public Digraph reverse()
{
Digraph R = new Digraph(V);
for (int v = 0; v < V; v++)
foreach (var w in getAdj(v))
R.addEdge(w, v);
return R;
}
public DirectedCycle(Digraph g)
{
marked = new bool[g.V];
onStack = new bool[g.V];
cycle = new Stack<int>(g.V);
edgeTo = new int[g.V];
for (int v = 0; v < g.V; v++)
if (!marked[v])
dfs(g, v);
}
private void dfs(Digraph g, int v)
{
marked[v] = true;
foreach (var w in g.getAdj(v))
{
if (!marked[w])
dfs(g, w);
}
order.Push(v);
}
private char[] find(String[] orderStrings)
{
Digraph g = new Digraph(26);
int j = 0;
for (int i = 0; i < orderStrings.Length - 1; i++)
{
string high = orderStrings[i + 1];
string low = orderStrings[i];
int minLength = Math.Min(low.Length, high.Length);
for (j = 0; j < minLength; j++)
{
if (low[j] == high[j])
continue;
if (low[j] != high[j])
g.addEdge(get(low[j]), get(high[j]));
}
}
DirectedCycle cycle = new DirectedCycle(g);
if (cycle.hasCycle()) {
foreach (var c in cycle.getCycle())
Console.Write(c + " -> ");
Console.WriteLine();
return null;
}
List<char> orders = new List<char>();
DFSDiagraph dfs = new DFSDiagraph(g);
foreach (var v in dfs.sort()) {
orders.Add(get(v));
}
return orders.ToArray();
}
private void dfs(Digraph g, int v)
{
marked[v] = true;
onStack[v] = true;
foreach (int w in g.getAdj(v))
{
if(hasCycle()) return;
else if (!marked[w])
{
edgeTo[w] = v;
dfs(g, w);
}
else if (onStack[w])
{
for (int x = v; x != w; x = edgeTo[x])
cycle.Push(x);
cycle.Push(w);
cycle.Push(v);
}
}
onStack[v] = false;
}
