44 lines
1.4 KiB
C++
44 lines
1.4 KiB
C++
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namespace tarjan {
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vector<int> scc(const vector<vector<int>>& ch) {
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int n = ch.size();
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int cnt = 0, scn = 0;
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vector<int> dfn(n), low(n), vis(n), st;
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vector<int> br(n);
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auto tarjan = [&] (auto tarjan, int v) -> void {
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dfn[v]=low[v]=++cnt;
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st.push_back(v);
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vis[v]=1;
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for(const auto&u:ch[v])
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if(!dfn[u]) tarjan(tarjan, u),low[v]=min(low[v],low[u]);
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else if(vis[u])low[v]=min(low[v],dfn[u]);
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if(dfn[v]==low[v]){
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++scn;
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int u;
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do u=st.back(), st.pop_back(),vis[u]=0,br[u]=scn; while(u!=v);
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}
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};
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for (int i = 0; i < n; ++i) {
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if (!dfn[i]) {
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tarjan(tarjan, i);
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}
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}
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return br;
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}
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vector<vector<int>> build_scc(const vector<vector<int>>& ch) {
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int n = ch.size();
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auto br = scc(ch);
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int cnt = *max_element(br.begin(), br.end());
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vector<unordered_set<int, safe_hash>> rb(cnt + 1);
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for (int i = 0; i < n; ++i) {
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for (auto&& u : ch[i]) {
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rb[br[i]].emplace(br[u]);
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}
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}
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vector<vector<int>> res(cnt + 1);
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for (int i = 1; i <= cnt; ++i) {
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res[i] = vector<int>(rb[i].begin(), rb[i].end());
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}
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return res;
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}
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}
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