无向图判断是否有环并输出环_无向图环输出-CSDN博客

本文链接：https://blog.csdn.net/speroc/article/details/105175319

void dfsVisit(vector<vector<int> >&graph, int node, vector<int>&visit,
               vector<int>&father)
{
    int n = graph.size();
    visit[node] = 1;//正在遍历状态
    //cout<<node<<"-\n";
    for(int i = 0; i < n; i++)
        if(i != node/*防止寻找自己*/ && graph[node][i] != INT_MAX/*防止两节点之间无边*/)
        {
            if(visit[i] == 1 && i != father[node]/*无向图如果i是node的父节点则不是环*/)
            //找到一个环
            {
                int tmp = node;
                cout<<"cycle: ";
                while(tmp != i)
                {
                    cout<<tmp<<"->";
                    tmp = father[tmp];
                }
                cout<<tmp<<endl;
            }
            else if(visit[i] == 0)//未遍历过
            {
                father[i] = node;
                dfsVisit(graph, i, visit, father);
            }
        }
    visit[node] = 2;//已经遍历过
}
 
void dfs(vector<vector<int> >&graph)
{
    int n = graph.size();
    vector<int> visit(n, 0); //visit按照算法导论22.3节分为三种状态0,1,2
    vector<int> father(n, -1);// father[i] 记录遍历过程中i的父节点
    for(int i = 0; i < n; i++)
        if(visit[i] == 0)
            dfsVisit(graph, i, visit, father);
}
/*dfs拓扑*/
stack<int> tuopu;
 
void dfsVisit(vector<vector<int> >&graph, int node, vector<int>&visit,
               vector<int>&father)
{
    int n = graph.size();
    visit[node] = 1;
    //cout<<node<<"-\n";
    for(int i = 0; i < n; i++)
        if(i != node && graph[node][i] != INT_MAX)
        {
            if(visit[i] == 1 && i != father[node])//找到一个环
            {
                int tmp = node;
                cout<<"cycle: ";
                while(tmp != i)
                {
                    cout<<tmp<<"->";
                    tmp = father[tmp];
                }
                cout<<tmp<<endl;
            }
            else if(visit[i] == 0)
            {
                father[i] = node;
                dfsVisit(graph, i, visit, father);
            }
        }
    visit[node] = 2;
    tuopu.push(node);
}
 
void dfs(vector<vector<int> >&graph)
{
    int n = graph.size();
    vector<int> visit(n, 0); //visit按照算法导论22.3节分为三种状态
    vector<int> father(n, -1);// father[i] 记录遍历过程中i的父节点
    for(int i = 0; i < n; i++)
        if(visit[i] == 0)
            dfsVisit(graph, i, visit, father);
}