private void dfs(GraphDigraph g, int v)
{
// 将顶点v设置成已搜索
this.markeds[v] = true;
// 把当前顶点进栈
this.onStack[v] = true;
// 进行深度搜索
IEnumerator ie = g.adjGet(v).GetEnumerator();
while (ie.MoveNext())
{
int w = (int)ie.Current;
if (!this.markeds[w])
{
dfs(g, w);
}
else
{
// 判断当前顶点是否已经在栈中， true表示是环，
if (this.onStack[w])
{
this.hasCycleBool = true;
return;
}
}
}
// 把当前顶点出栈
this.onStack[v] = false;
}
/// <summary>
/// 构造拓扑排序对象
/// </summary>
/// <param name="g">有向图</param>
public TopoLogicalOrder(GraphDigraph g)
{
// 检测图是否有环
GraphDirectedCyle cycle = new GraphDirectedCyle(g);
bool hasCycle = cycle.hasCycle();
if (!hasCycle)
{
DepthFirstOrder depth = new DepthFirstOrder(g);
orderStack = depth.reversePost();
}
}
/// <summary>
/// 创建一个顶点排序对象 生成顶点线性队列
/// </summary>
/// <param name="g"></param>
public DepthFirstOrder(GraphDigraph g)
{
// 初始markeds 数组
this.markeds = new bool[g.countV()];
// 初始化 reversePost stack 栈
this.reversePostStack = new StackList <int>();
// 遍历图中的每一个顶点，让每一个定点做作为入口，完成一次深度优先搜索
for (int v = 0; v < g.countV(); v++)
{
if (!this.markeds[v])
{
dfs(g, v);
}
}
}
/// <summary>
/// 基于深度优先搜索，生成顶点线性排序
/// </summary>
/// <param name="g"></param>
/// <param name="v"></param>
private void dfs(GraphDigraph g, int v)
{
// 标记当前v已经被搜索
this.markeds[v] = true;
// 通过循环深度搜索v
IEnumerator ie = g.adjGet(v).GetEnumerator();
while (ie.MoveNext())
{
int w = (int)ie.Current;
if (!this.markeds[w])
{
dfs(g, w);
}
}
// 让当前这个顶点进栈
this.reversePostStack.push(v);
}
private GraphDigraph reverse()
{
// 创建图
GraphDigraph g = new GraphDigraph(this.V);
// 添加边， 遍历原图的每个顶点
for (int v = 0; v < this.V; v++)
{
// 获取由该顶点v指出的所有的边
IEnumerator ie = this.adj[v].GetEnumerator();
while (ie.MoveNext())
{
// 原图中表示的是由顶点v->w的边
int w = (int)ie.Current;
g.addEdge(w, v);
}
}
return(g);
}
public GraphDirectedCyle(GraphDigraph g)
{
// 初始化 markeds 数组
this.markeds = new bool[g.countV()];
// 初始化 hasCycleBool
this.hasCycleBool = false;
//初始化onStack
this.onStack = new bool[g.countV()];
// 找到图中每一个顶点 让每一个顶点作为入口调用一次 dfs 函数
for (int v = 0; v < g.countV(); v++)
{
// 如果当前顶点 还没有搜索过 则调用dfs搜索
if (!this.markeds[v])
{
dfs(g, v);
}
}
}
/// <summary>
/// 拓扑排序 测试
/// </summary>
private static void TopoLogicalOrderTest()
{
// 准备有向图
GraphDigraph graph = new GraphDigraph(6);
graph.addEdge(0, 2);
graph.addEdge(0, 3);
graph.addEdge(1, 3);
graph.addEdge(2, 4);
graph.addEdge(3, 4);
graph.addEdge(4, 5);
// 通过TopoLogicalOrder对象排序
TopoLogicalOrder order = new TopoLogicalOrder(graph);
if (!order.isCycle())
{
StackList <int> stack = order.order();
// 获取顶点线性排序的打印
if (stack != null)
{
IEnumerator ie = stack.GetEnumerator();
while (ie.MoveNext())
{
int o = (int)ie.Current;
Console.Write(o + ",");
}
}
else
{
Console.WriteLine("TopoLogicalOrder stack is null.");
}
}
else
{
Console.WriteLine("has cycle.");
}
}