void tarjan_dfs(int u)
{
dfn[u] = low[u] = ++idx;
in_stack[u] = 1;
stack_push_back(u);
struct Edge *e = orig_edge[u];
while (e) {
if (!dfn[e->v]) {
tarjan_dfs(e->v);
if (low[e->v] < low[u]) low[u] = low[e->v];
}
else if (in_stack[e->v])
if (dfn[e->v] < low[u]) low[u] = dfn[e->v];
e = e->next;
}
if (dfn[u] == low[u]) {
scc_cnt++;
int v;
do {
v = stack_back();
stack_pop_back();
in_stack[v] = 0;
scc_id[v] = scc_cnt;
scc_size[scc_cnt]++;
} while (v != u) ;
}
}
void tarjan_scc(int num_v = MAXV) {
visiting = stack<int>();
memset(visited, 0, sizeof visited);
cur_num = cur_comp = 0;
for(int i = 0; i < num_v; ++i)
if(!visited[i])
tarjan_dfs(i);
}
void tarjan(int n)
{
idx = scc_cnt = 0;
memset(dfn, 0, sizeof(dfn));
memset(low, 0, sizeof(low));
memset(scc_id, 0, sizeof(scc_id));
memset(scc_size, 0, sizeof(scc_size));
int i;
for (i = 1; i <= n; i++)
if (!dfn[i]) tarjan_dfs(i);
}
int tarjan_dfs(int v) {
lowest[v] = num[v] = cur_num++;
visiting.push(v);
visited[v] = 1;
for(int i = last_edge[v]; i != -1; i = prev_edge[i]) {
int w = adj[i];
if(visited[w] == 0) lowest[v] = min(lowest[v], tarjan_dfs(w));
else if(visited[w] == 1) lowest[v] = min(lowest[v], num[w]);
}
if(lowest[v] == num[v]) {
int last = -1;
while(last != v) {
comp[last = visiting.top()] = cur_comp;
visited[last] = 2;
visiting.pop();
}
++cur_comp;
}
return lowest[v];
}