/// <summary>
/// 有向グラフの強連結成分を判定する
/// </summary>
/// <param name="graph">グラフ</param>
/// <returns>ノード→クラスタID配列</returns>
public static int[] Calc(DirectedAdjacencyList graph)
{
var results = Visit(graph);
int[] cluster_array = AntiVisit(graph, results.invOrderArray);
return(cluster_array);
}
/// <summary>
/// 正方向の後順探索で各接点に訪問する
/// </summary>
/// <param name="graph">グラフ</param>
/// <returns>ノード→訪問順配列と、訪問順→ノード配列</returns>
private static (int[] orderArray, int[] invOrderArray) Visit(DirectedAdjacencyList graph)
{
// 作業領域を確保
int[] order_array = new int[graph.NodeNum];
int[] inv_order_array = new int[graph.NodeNum];
for (int i = 0; i < graph.NodeNum; i++)
{
order_array[i] = UNVISITED;
}
int order = 0;
Stack <int> visit_stack = new Stack <int>(graph.NodeNum);
for (int i = 0; i < graph.NodeNum; i++)
{
// 未訪問のノードから始める
if (order_array[i] != UNVISITED)
{
continue;
}
visit_stack.Clear();
visit_stack.Push(i);
order_array[i] = VISITED;
while (visit_stack.Count != 0)
{
int v = visit_stack.Peak();
// vから到達できる未訪問のノードに訪問する
bool move = false;
LinkList edgeList = graph.GetOutLinkedEdgeList(v);
for (LinkNode node = edgeList.head; node != null; node = node.next)
{
int w = GraphUtil.GetOpposite(v, graph.EdgeList[node.data]);
if (order_array[w] == UNVISITED)
{
visit_stack.Push(w);
order_array[w] = VISITED;
move = true;
}
}
// どこにも移動できなかったら後順探索に従って番号付け
if (!move)
{
visit_stack.Pop();
order_array[v] = order;
inv_order_array[order] = v;
order++;
}
}
}
return(order_array, inv_order_array);
}
/// <summary>
/// 逆方向の前順探索で各接点に訪問する
/// </summary>
/// <param name="graph">グラフ</param>
/// <param name="invOrderArray">訪問順→ノード配列</param>
/// <returns>ノード→クラスタID配列</returns>
public static int[] AntiVisit(DirectedAdjacencyList graph, int[] invOrderArray)
{
int[] result = new int[graph.NodeNum];
for (int i = 0; i < result.Length; i++)
{
result[i] = UNVISITED;
}
int cluster_id = 0;
Stack <int> visit_stack = new Stack <int>(graph.NodeNum);
for (int i = 0; i < graph.NodeNum; i++)
{
// i番目に大きい訪問順を持つノードから始める
int s = invOrderArray[(graph.NodeNum - 1) - i];
// 訪問済みならスキップ
if (result[s] != UNVISITED)
{
continue;
}
visit_stack.Clear();
visit_stack.Push(s);
result[s] = cluster_id;
while (visit_stack.Count != 0)
{
int v = visit_stack.Pop();
// 反有向木において、vから到達できる未訪問のノードに訪問する
LinkList edgeList = graph.GetInLinkedEdgeList(v);
for (LinkNode node = edgeList.head; node != null; node = node.next)
{
int w = GraphUtil.GetOpposite(v, graph.EdgeList[node.data]);
if (result[w] == UNVISITED)
{
visit_stack.Push(w);
result[w] = cluster_id;
}
}
}
cluster_id++;
}
return(result);
}
public void BasicTests()
{
var adjList = new DirectedAdjacencyList <int>(2);
adjList.AddVertex(10);
adjList.AddVertex(20);
adjList.CreateEdge(10, 20);
Assert.IsTrue(adjList.Adjacent(10, 20));
Assert.IsFalse(adjList.Adjacent(20, 10));
var undirectedList = new UndirectedAdjacenyList <int>(2);
undirectedList.AddVertex(10);
undirectedList.AddVertex(20);
undirectedList.CreateEdge(10, 20);
Assert.IsTrue(undirectedList.Adjacent(10, 20));
Assert.IsTrue(undirectedList.Adjacent(20, 10));
}
public static AdjacencyList ReadGraph(string filepath)
{
StreamReader reader = new StreamReader(filepath);
int no_of_node = -1;
int no_of_edge = -1;
bool directed = false;
while (!reader.EndOfStream)
{
string[] record = reader.ReadLine().Split(' ');
// 1フィールド目が属性
switch (record[0])
{
case "TYPE":
directed = record[2] == "DIRECTED";
break;
case "NO_OF_NODE":
no_of_node = int.Parse(record[2]);
break;
case "NO_OF_EDGE":
no_of_edge = int.Parse(record[2]);
break;
case "EDGE_CODE_SECTION":
goto READ_EDGE_DATA;
}
}
// エッジデータの読み込み
READ_EDGE_DATA:
if (no_of_node == -1)
{
Common.ErrorExit("ノード数の指定がありません。");
}
if (no_of_edge == -1)
{
Common.ErrorExit("エッジ数の指定がありません。");
}
int[][] edge_list = new int[no_of_edge][];
for (int i = 0; i < no_of_edge; i++)
{
if (reader.EndOfStream)
{
Common.ErrorExit("NO_OF_EDGEで指定されたエッジ数よりも少ないデータが記載されています。");
}
string[] record = reader.ReadLine().Split(' ');
edge_list[i] = new int[2];
edge_list[i][0] = int.Parse(record[0]);
edge_list[i][1] = int.Parse(record[1]);
}
if (!reader.EndOfStream)
{
Common.ErrorExit("NO_OF_EDGEで指定されたエッジ数よりも多いデータが記載されています。");
}
AdjacencyList instance;
if (directed)
{
instance = new DirectedAdjacencyList(no_of_node, no_of_edge, edge_list);
}
else
{
instance = new UndirectedAdjacencyList(no_of_node, no_of_edge, edge_list);
}
return(instance);
}