void scc_dfs(const vector<vector<int> > &g, int u, bool addToStack = false) {
for (int i = 0; i < (int)g[u].size(); ++i) {
int v = g[u][i];
if (scc[v] == inf) {
scc[v] = scc[u];
scc_dfs(g, v, addToStack);
}
}
if (addToStack) S.push(u);
}
int kosaraju() {
const int inf = int(1e9 + 7);
int ans = 0;
scc.assign(n, inf);
for (int u = 0; u < n; ++u) {
if (scc[u] != inf) continue;
scc[u] = true;
scc_dfs(g, u, true);
}
scc.assign(n, inf);
while (!S.empty()) {
int u = S.top();
S.pop();
if (scc[u] != inf) continue;
scc[u] = ans++;
scc_dfs(gt, u);
}
return ans;
}
pair<union_find, vi> scc(const vvi &adj) {
int n = size(adj), u, v;
order.clear();
union_find uf(n); vi dag; vvi rev(n);
rep(i,0,n) rep(j,0,size(adj[i])) rev[adj[i][j]].push_back(i);
visited.resize(n);
fill(visited.begin(), visited.end(), false);
rep(i,0,n) if (!visited[i]) scc_dfs(rev, i);
fill(visited.begin(), visited.end(), false);
stack<int> S;
for (int i = n-1; i >= 0; i--) {
if (visited[order[i]]) continue;
S.push(order[i]), dag.push_back(order[i]);
while (!S.empty()) {
visited[u = S.top()] = true, S.pop();
uf.unite(u, order[i]);
rep(j,0,size(adj[u]))
if (!visited[v = adj[u][j]]) S.push(v); } }
return pair<union_find, vi>(uf, dag); }
void scc_dfs(const vvi &adj, int u) {
int v; visited[u] = true;
rep(i,0,size(adj[u]))
if (!visited[v = adj[u][i]]) scc_dfs(adj, v);
order.push_back(u); }
