refactor: better v_bcc

src/code/graph/v_bcc.hpp

@@ -1,47 +1,47 @@
 #ifndef TIFALIBS_GRAPH_V_BCC
 #define TIFALIBS_GRAPH_V_BCC
 
-#include "../util/util.hpp"
+#include "alist.hpp"
 
 namespace tifa_libs::graph {
 
-template <class EW>
-class v_bcc {
-  vvec<EW> CR g;
-
- public:
-  u32 id;
+template <bool get_cut = false, bool get_belongs = true>
+struct v_bcc {
   vecu dfn, low;
-  vecb cut;
   vvecu belongs;
+  vecb cut;
 
-  //! EW need rev_edge
-  CEXPE v_bcc(cT_(vvec<EW>) G) NE : g(G) { build(); }
-
-  CEXP void build() NE {
-    u32 cnt = 0, n = u32(g.size());
-    id = 0, dfn = low = vecu(n, n), cut = vecb(n, 0);
-    vecu s;
-    auto dfs = [&](auto &&dfs, u32 u, u32 fa, u32 inv_from) NE -> void {
-      dfn[u] = low[u] = cnt++;
-      if (u == fa && g[u].size() == 0) cut[u] = 1, belongs.push_back(vecu(1, u)), ++id;
-      s.push_back(u);
-      flt_ (u32, i, 0, (u32)g[u].size()) {
-        auto v = g[u][i];
-        if (v.to == fa && i == inv_from) continue;
-        if (dfn[v.to] == n) {
-          if (dfs(dfs, v.to, u, v.inv), low[u] = min(low[u], low[v.to]); low[v.to] >= dfn[u]) {
-            u32 p;
-            cut[u] = 1, belongs.push_back(vecu(1, u));
-            do p = s.back(), s.pop_back(), belongs[id].push_back(p);
-            while (p != v.to);
-            ++id;
+  //! G should be undirect
+  template <bool with_deg>
+  CEXP v_bcc(alist<with_deg> CR g) NE : dfn(g.size()), low(g.size()) {
+    if CEXP (get_cut) cut = vecb(g.size());
+    vecu stk;
+    u32 cnt = 0, start;
+    auto tarjan = [&](auto&& f, u32 u, u32 fa) -> void {
+      u32 son = 0;
+      low[u] = dfn[u] = ++cnt;
+      if CEXP (get_belongs) stk.push_back(u);
+      for (auto v : g[u])
+        if (!dfn[v]) {
+          ++son, f(f, v, u), low[u] = min(low[u], low[v]);
+          if (low[v] >= dfn[u]) {
+            if CEXP (get_cut)
+              if (u != start) cut[u] = true;
+            if CEXP (get_belongs) {
+              vecu now;
+              now.reserve(stk.size() + 1);
+              while (!stk.empty() && (now.empty() || now.back() != v)) now.push_back(stk.back()), stk.pop_back();
+              now.push_back(u), now.shrink_to_fit(), belongs.push_back(now);
+            }
           }
-        } else low[u] = min(low[u], dfn[v.to]);
-      }
+        } else if (v != fa) low[u] = min(low[u], dfn[v]);
+      if CEXP (get_cut)
+        if (u == start && son >= 2) cut[u] = true;
+      if CEXP (get_belongs)
+        if (!~fa && !son) belongs.push_back({u});
     };
-    flt_ (u32, i, 0, n)
-      if (dfn[i] == n) dfs(dfs, i, i, -1_u32);
+    flt_ (u32, i, 0, g.size())
+      if (!dfn[i]) tarjan(tarjan, start = i, -1_u32);
   }
 };
 

src/test_cpverifier/aizu-grl/grl_3_a.test.cpp

@@ -0,0 +1,18 @@
+#define PROBLEM "https://onlinejudge.u-aizu.ac.jp/courses/library/5/GRL/all/GRL_3_A"
+
+#include "../../code/graph/v_bcc.hpp"
+
+int main() {
+  std::cin.tie(nullptr)->std::ios::sync_with_stdio(false);
+  u32 n, m;
+  std::cin >> n >> m;
+  tifa_libs::graph::alist g(n);
+  for (u32 i = 0, u, v; i < m; ++i) {
+    std::cin >> u >> v;
+    g.add_arc(u, v), g.add_arc(v, u);
+  }
+  tifa_libs::graph::v_bcc<true, false> bcc(g);
+  flt_ (u32, i, 0, n)
+    if (bcc.cut[i]) std::cout << i << '\n';
+  return 0;
+}

src/test_cpverifier/library-checker-graph/biconnected_components.test.cpp

@@ -6,20 +6,14 @@ int main() {
   std::cin.tie(nullptr)->std::ios::sync_with_stdio(false);
   u32 n, m;
   std::cin >> n >> m;
-  struct EW {
-    u32 to, inv;
-  };
-  vvec<EW> e(n);
+  tifa_libs::graph::alist g(n);
   for (u32 i = 0, u, v; i < m; ++i) {
     std::cin >> u >> v;
-    if (u == v) continue;
-    u32 tem1 = u32(e[u].size()), tem2 = u32(e[v].size());
-    e[u].push_back({v, tem2});
-    e[v].push_back({u, tem1});
+    g.add_arc(u, v), g.add_arc(v, u);
   }
-  tifa_libs::graph::v_bcc<EW> bcc(e);
-  std::cout << bcc.id << '\n';
-  for (u32 i = 0; i < bcc.id; ++i) {
+  tifa_libs::graph::v_bcc bcc(g);
+  std::cout << bcc.belongs.size() << '\n';
+  for (u32 i = 0; i < bcc.belongs.size(); ++i) {
     std::cout << bcc.belongs[i].size() << ' ';
     for (auto x : bcc.belongs[i])
       std::cout << x << ' ';

src/test_tinplate/graph/v_bcc.cpp

@@ -6,21 +6,17 @@ int main() {
   std::cin.tie(nullptr)->std::ios::sync_with_stdio(false);
   u32 n, m;
   std::cin >> n >> m;
-  struct EW {
-    u32 to, inv;
-  };
-  vvec<EW> e(n);
+  tifa_libs::graph::alist g(n);
   for (u32 i = 0, u, v; i < m; ++i) {
     std::cin >> u >> v;
-    if (--u, --v; u == v) continue;
-    u32 tem1 = u32(e[u].size()), tem2 = u32(e[v].size());
-    e[u].push_back({v, tem2}), e[v].push_back({u, tem1});
+    --u, --v;
+    g.add_arc(u, v), g.add_arc(v, u);
   }
-  tifa_libs::graph::v_bcc<EW> bcc(e);
-  std::cout << bcc.id << '\n';
-  flt_ (u32, i, 0, bcc.id) {
-    std::cout << bcc.belongs[i].size() << ' ';
-    for (auto x : bcc.belongs[i]) std::cout << x + 1 << ' ';
+  tifa_libs::graph::v_bcc bcc(g);
+  std::cout << bcc.belongs.size() << '\n';
+  flt_ (u32, i, 0, (u32)bcc.belongs.size()) {
+    std::cout << bcc.belongs[i].size();
+    for (auto x : bcc.belongs[i]) std::cout << ' ' << x + 1;
     std::cout << '\n';
   }
 }