我正在使用递归回溯寻找周期向图。有一个建议伪code这个这里，这是在这里：

I am working on finding cycles in directed graph using recursive backtracking. There is a suggested pseudocode for this here, which is here:

dfs(adj,node,visited):  
  if (visited[node]):  
    if (node == start):  
      "found a path"  
    return;  
  visited[node]=YES;  
  for child in adj[node]:  
    dfs(adj,child,visited)
  visited[node]=NO;

调用上述功能的起始节点：

Call the above function with the start node:

visited = {}
dfs(adj,start,visited)

虽然这不是最有效的算法相比， Tarjans算法，这就够了我简单的让我明白了。目前，该code没有检测到循环次数的计数。

While this is not the most efficient algorithm when compared to Tarjans algorithm, this is simple enough me for me to understand. Currently, this code does not have a count of number cycles detected.

我用Java实现的：

//this is the main method that calls the helper DFS which runs on each node
public int allCyclesDirectedmain(){
    //this initializes all vertices
    clearAll();
    int[] count = new int[1];
    for (Vertex v: vertexMap.values()){
        //System.out.println(v.name);
        //clearAll();
        dfs(v,v,count);
    }
    return count[0];
}

//start and v are same when the method first fires.
public void dfs(Vertex start, Vertex v,int[] count){
   if (v.isVisited){
       if (start==v){
           //found a path
           count[0]++;
       }
       return ;
   }
   v.setVisited(true);
   for (Edge e : v.adj){
       Vertex next = e.target;
       dfs(start,next,count);
   }
   v.setVisited(false);
}

有关的图，下面边： （1 2），（2 3），（3 1），（2 5），（5,6），（6 2） - 我得到6个周期的输出

For the graph with following edges: (1 2),(2 3),(3 1),(2 5),(5 6),(6 2)-- I get 6 cycles as output.

（1 2），（2 3），（3〜4），（4,1），（2 5），（5,6），（6 2） - 我得到7个循环输出

(1 2),(2 3),(3 4),(4,1),(2 5),(5 6),(6 2) -- I get 7 cycles as output.

我可以看到我目前的code做循环检测每个顶点已经pviously检测周期一个$ P $的一部分（例如：具有三个节点一个周期给我三个周期，而这必须每个节点为一个）。我在这里需要一些技巧，以什么错误以及一些修复。

I can see that my current code does cycle detection for each vertex that are already part of a previously detected cycle (e.g.: a cycle with three nodes gives me three cycles for each individual nodes while this must be one). I need some tips here as to what is going wrong and some fix.

推荐答案

有关（1 2），（2 3），（3 1），你打电话

所以，你数着相同的周期多次。

So you're counting the same cycle multiple times.

最简单的修复我能想到的是简单地设置了访问标志 DFS 通话后。

The simplest fix I can think of is simply setting the visited flag after the dfs call.

public int allCyclesDirectedmain(){
    clearAll();
    int[] count = new int[1];
    for (Vertex v: vertexMap.values()){
        dfs(v,v,count);
        v.setVisited(true); // <---
    }
    return count[0];
}