Tarjan 基础用法 (仅代码版)

struct Tarjan
{
    int dfn[maxn], low[maxn], Time;
    bool vis_cutnode[maxn], vis_bridge[maxn];

    combo Tarjan_gd(int u, int fa)
    {//有/无 向图的割点
        dfn[u] = low[u] = ++ Time;
        int cnt = 0;
        for (int i = heade[u]; i; i = e[i].next)
        {
            int v = e[i].to;
            if(! dfn[v])
            {
                Tarjan_gd(v, u);
                low[u] = min(low[u], low[v]);
                if(low[v] >= dfn[u])
                {
                    cnt ++;
                    if(fa != 0 || cnt > 1)
                    {
                        vis_cutnode[u] = true;
                    }
                }
                else 
                {
                    low[u] = min(low[u], dfn[v]);
                }
            }
        }
        return;
    }

    combo Tarjan_gb(int u, int id_edge)
    {//有/无 向图的割边
        dfn[u] = low[u] = ++ Time;
        for (int i = heade[u]; i; i = e[i].next)
        {
            int v = e[i].to;
            if(i == id_edge ^ 1) continue;
            if(! dfn[v])
            {
                Tarjan_gb(v, i);
                low[u] = min(low[u], low[v]);
                if(low[v] > dfn[u])
                {   
                    vis_bridge[i] = vis_bridge[i ^ 1] = true; 
                }
            }
            else 
            {
                low[u] = min(low[u], dfn[v]);
            }
        }
        return;
    }

    //SD//缩点 (有向图)
    int st[maxn], top, tot_s;
    int belong[maxn];
    combo Tarjan_sd(int u)//缩点 (有向图)
    {
        dfn[u] = low[u] = ++ Time;
        st[++ top] = u;
        for (int i = heade[u]; i; i = e[i].next)
        {
            int v = e[i].to;
            if(!dfn[v])
            {
                Tarjan_sd(v);
                low[u] = min(low[u], low[v]);
            }
            else 
            {
                low[u] = min(low[u], dfn[v]);
            }
        } 
        if(dfn[u] == low[u])
        {
            tot_s ++;
            while(st[top + 1] != u)
            {
                belong[st[top --]] = tot_s;   
            }
        }
        return;
    }
    
    //v_DCC//点双联通分量 (无向图)
    int num, tot_v;
    int new_id[maxn]\;
    vector <int> v_dcc[maxn];
    combo Tarjan_ds(int u, int fa)
    {//无向图的点双联通分量 v_DCC
        dfn[u] = low[u] = ++ Time;
        st[++ top] = u;
        if(fa == 0 && heade[u] == 0)
        {
            v_dcc[++ tot_v].push_back(u);
            return;
        }
        int cnt = 0;
        for (int i = heade[u]; i; i = e[i].next)
        {
            int v = e[i].to;
            if(! dfn[v])
            {
                Tarjan_ds(v, u);
                low[u] = min(low[u], low[v]);
                if(low[v] >= dfn[u])
                {
                    cnt ++;
                    if(fa != 0 || cnt > 0) vis_cutnode[u] = true;
                    while(st[top + 1] != v)
                    {
                        v_dcc[++ tot_v].push_back(st[top --]);
                    }   
                }
            }
            else 
            {
                low[u] = min(low[u], dfn[v]);
            }
        }
        return;
    }
    combo get_ds_sd()
    {
        num = tot_v;
        for (int i = 1; i <= n; ++ i)
        {
            if(vis_cutnode[i])
            {
                new_id[i] = ++ num;
            }
        }
        for (int i = 1; i <= tot_v; ++ i)
        {
            for (int j = 0; j < v_dcc[i].size(); ++ j)
            {
                int u = v_dcc[i][j];
                if(vis_cutnode[u])
                {
                    Insertg(i, new_id[u]), Insertg(new_id[u], i);
                }
                else 
                {
                    belong[u] = i;
                }
            }
        }
        return;
    }

    //e_DCC//边双联通分量 (无向图)
    int e_DCC[maxn], tot_e;
    combo Dfs_e_DCC(int u)
    {
        e_DCC[u] = tot_e;
        for (int i = heade[u]; i; i = e[i].next)
        {
            int v = e[i].to;
            if(e_DCC[v] || vis_bridge[i]) continue;
            Dfs_e_DCC(v);
        }
    }
    combo get_bs()
    {//无向图的边双联通分量 e_DCC
        for (int i = 1; i <= n; ++ i)
        {
            if(!e_DCC[i])
            {
                ++ tot_e; Dfs_e_DCC(i);
            }
        }
        return;
    }
    combo get_bs_sd()
    {//边双联通分量的缩点
        for (int i = 2; i <= tote; ++ i)
        {
            int u = e[i ^ 1].to, v = e[i].to;
            if(e_DCC[u] == e_DCC[v]) continue;
            Insertg(u, v); 
        }
    }

}T;