ACM模板——强连通分量

vector<int> G[maxn];
vector<int> rG[maxn];
vector<int> vs;
vector<int> ans[maxn];
bool used[maxn];
int V,E;
int rnt = 0;
void add_edge(int from,int to)
{
    G[from].pb(to);
    rG[to].pb(from);
}
void dfs(int v)
{
    used[v] = true;
    _for(i,0,G[v].size())
        if(!used[G[v][i]])
            dfs(G[v][i]);
    vs.pb(v);
}
void rdfs(int v,int k)
{
    used[v] = true;
    ans[k].pb(v);
    _for(i,0,rG[v].size())
        if(!used[rG[v][i]])
            rdfs(rG[v][i],k);
}
//第k个集合里有哪些节点 ans[k]
//rnt为最大集合的集合大小
void Kosaraju()
{
    memset(used,0,sizeof(used));
    _for(v,1,V+1)
        if(!used[v])
            dfs(v);
    
    memset(used,0,sizeof(used));
    int k = 0;
    _rep(i,vs.size()-1,-1)
        if(!used[vs[i]])
        {
            rdfs(vs[i],k);
            rnt = max(rnt,(int)ans[k].size());
            k ++;
        }
}

int N,M;
int ver[maxn],Next[maxn],head[maxn],dfn[maxn],low[maxn];
int Gver[maxn],GNext[maxn],Ghead[maxn],Gtot;
int stack[maxn],ins[maxn],c[maxn];
vector<int> scc[maxn];
int tot,top,cnt,nm;
//cnt个强连通分量，scc[i]记录编号为i的强连通分量中的所有节点，c[x]表示x所在连通分量地区
void addori(int x,int y)
{
    ver[++tot] = y,Next[tot] = head[x],head[x] = tot;
}
void tarjan(int x)
{
    dfn[x] = low[x] = ++nm;
    stack[++top] = x,ins[x] = 1;
    for(int i = head[x]; i; i = Next[i])
    {
        int y = ver[i];
        if(!dfn[y])
        {
            tarjan(y);
            low[x] = min(low[x],low[y]);
        }
        else if(ins[y])
            low[x] = min(low[x],dfn[y]);
    }
    if(dfn[x] == low[x])
    {
        cnt ++;
        int y;
        do
        {
            y = stack[top --],ins[y] = 0;
            c[y] = cnt,scc[cnt].pb(y);
        }
        while(x != y);
    }
}
void addAft(int x,int y)
{
    Gver[++Gtot] = y;
    GNext[Gtot] = Ghead[x];
    Ghead[x] = Gtot;
}
void Shrink()
{
    _for(i,1,N+1)
    if(!dfn[i])
        tarjan(i);

    _for(x,1,N+1)
    for(int i = head[x]; i; i = Next[i])
    {
        int y = ver[i];
        if(c[x]==c[y]) continue;
        addAft(c[y],c[x]);
    }
}