#line 1 "graph/test/dulmage_mendelsohn.yuki1744.test.cpp" #define PROBLEM "https://yukicoder.me/problems/no/1744" #line 2 "graph/bipartite_matching.hpp" #include #include #include // Bipartite matching of undirected bipartite graph (Hopcroft-Karp) // https://ei1333.github.io/luzhiled/snippets/graph/hopcroft-karp.html // Comprexity: O((V + E)sqrtV) // int solve(): enumerate maximum number of matching / return -1 (if graph is not bipartite) struct BipartiteMatching { int V; std::vector> to; // Adjacency list std::vector dist; // dist[i] = (Distance from i'th node) std::vector match; // match[i] = (Partner of i'th node) or -1 (No parter) std::vector used, vv; std::vector color; // color of each node(checking bipartition): 0/1/-1(not determined) BipartiteMatching() = default; BipartiteMatching(int V_) : V(V_), to(V_), match(V_, -1), used(V_), color(V_, -1) {} void add_edge(int u, int v) { assert(u >= 0 and u < V and v >= 0 and v < V and u != v); to[u].push_back(v); to[v].push_back(u); } void _bfs() { dist.assign(V, -1); std::vector q; int lq = 0; for (int i = 0; i < V; i++) { if (!color[i] and !used[i]) q.push_back(i), dist[i] = 0; } while (lq < int(q.size())) { int now = q[lq++]; for (auto nxt : to[now]) { int c = match[nxt]; if (c >= 0 and dist[c] == -1) q.push_back(c), dist[c] = dist[now] + 1; } } } bool _dfs(int now) { vv[now] = true; for (auto nxt : to[now]) { int c = match[nxt]; if (c < 0 or (!vv[c] and dist[c] == dist[now] + 1 and _dfs(c))) { match[nxt] = now, match[now] = nxt; used[now] = true; return true; } } return false; } bool _color_bfs(int root) { color[root] = 0; std::vector q{root}; int lq = 0; while (lq < int(q.size())) { int now = q[lq++], c = color[now]; for (auto nxt : to[now]) { if (color[nxt] == -1) { color[nxt] = !c, q.push_back(nxt); } else if (color[nxt] == c) { return false; } } } return true; } int solve() { for (int i = 0; i < V; i++) { if (color[i] == -1 and !_color_bfs(i)) return -1; } int ret = 0; while (true) { _bfs(); vv.assign(V, false); int flow = 0; for (int i = 0; i < V; i++) { if (!color[i] and !used[i] and _dfs(i)) flow++; } if (!flow) break; ret += flow; } return ret; } template friend OStream &operator<<(OStream &os, const BipartiteMatching &bm) { os << "{N=" << bm.V << ':'; for (int i = 0; i < bm.V; i++) { if (bm.match[i] > i) os << '(' << i << '-' << bm.match[i] << "),"; } return os << '}'; } }; #line 2 "graph/strongly_connected_components.hpp" #include #line 5 "graph/strongly_connected_components.hpp" // CUT begin // Directed graph library to find strongly connected components (強連結成分分解) // 0-indexed directed graph // Complexity: O(V + E) struct DirectedGraphSCC { int V; // # of Vertices std::vector> to, from; std::vector used; // Only true/false std::vector vs; std::vector cmp; int scc_num = -1; DirectedGraphSCC(int V = 0) : V(V), to(V), from(V), cmp(V) {} void _dfs(int v) { used[v] = true; for (auto t : to[v]) if (!used[t]) _dfs(t); vs.push_back(v); } void _rdfs(int v, int k) { used[v] = true; cmp[v] = k; for (auto t : from[v]) if (!used[t]) _rdfs(t, k); } void add_edge(int from_, int to_) { assert(from_ >= 0 and from_ < V and to_ >= 0 and to_ < V); to[from_].push_back(to_); from[to_].push_back(from_); } // Detect strongly connected components and return # of them. // Also, assign each vertex `v` the scc id `cmp[v]` (0-indexed) int FindStronglyConnectedComponents() { used.assign(V, false); vs.clear(); for (int v = 0; v < V; v++) if (!used[v]) _dfs(v); used.assign(V, false); scc_num = 0; for (int i = (int)vs.size() - 1; i >= 0; i--) if (!used[vs[i]]) _rdfs(vs[i], scc_num++); return scc_num; } // Find and output the vertices that form a closed cycle. // output: {v_1, ..., v_C}, where C is the length of cycle, // {} if there's NO cycle (graph is DAG) int _c, _init; std::vector _ret_cycle; bool _dfs_detectcycle(int now, bool b0) { if (now == _init and b0) return true; for (auto nxt : to[now]) if (cmp[nxt] == _c and !used[nxt]) { _ret_cycle.emplace_back(nxt), used[nxt] = 1; if (_dfs_detectcycle(nxt, true)) return true; _ret_cycle.pop_back(); } return false; } std::vector DetectCycle() { int ns = FindStronglyConnectedComponents(); if (ns == V) return {}; std::vector cnt(ns); for (auto x : cmp) cnt[x]++; _c = std::find_if(cnt.begin(), cnt.end(), [](int x) { return x > 1; }) - cnt.begin(); _init = std::find(cmp.begin(), cmp.end(), _c) - cmp.begin(); used.assign(V, false); _ret_cycle.clear(); _dfs_detectcycle(_init, false); return _ret_cycle; } // After calling `FindStronglyConnectedComponents()`, generate a new graph by uniting all vertices // belonging to the same component(The resultant graph is DAG). DirectedGraphSCC GenerateTopologicalGraph() { DirectedGraphSCC newgraph(scc_num); for (int s = 0; s < V; s++) for (auto t : to[s]) { if (cmp[s] != cmp[t]) newgraph.add_edge(cmp[s], cmp[t]); } return newgraph; } }; // 2-SAT solver: Find a solution for `(Ai v Aj) ^ (Ak v Al) ^ ... = true` // - `nb_sat_vars`: Number of variables // - Considering a graph with `2 * nb_sat_vars` vertices // - Vertices [0, nb_sat_vars) means `Ai` // - vertices [nb_sat_vars, 2 * nb_sat_vars) means `not Ai` struct SATSolver : DirectedGraphSCC { int nb_sat_vars; std::vector solution; SATSolver(int nb_variables = 0) : DirectedGraphSCC(nb_variables * 2), nb_sat_vars(nb_variables), solution(nb_sat_vars) {} void add_x_or_y_constraint(bool is_x_true, int x, bool is_y_true, int y) { assert(x >= 0 and x < nb_sat_vars); assert(y >= 0 and y < nb_sat_vars); if (!is_x_true) x += nb_sat_vars; if (!is_y_true) y += nb_sat_vars; add_edge((x + nb_sat_vars) % (nb_sat_vars * 2), y); add_edge((y + nb_sat_vars) % (nb_sat_vars * 2), x); } // Solve the 2-SAT problem. If no solution exists, return `false`. // Otherwise, dump one solution to `solution` and return `true`. bool run() { FindStronglyConnectedComponents(); for (int i = 0; i < nb_sat_vars; i++) { if (cmp[i] == cmp[i + nb_sat_vars]) return false; solution[i] = cmp[i] > cmp[i + nb_sat_vars]; } return true; } }; #line 5 "graph/dulmage_mendelsohn_decomposition.hpp" #include #line 7 "graph/dulmage_mendelsohn_decomposition.hpp" // Dulmage–Mendelsohn (DM) decomposition (DM 分解) // return: [(W+0, W-0), (W+1,W-1),...,(W+(k+1), W-(k+1))] // : sequence of pair (left vetrices, right vertices) // - |W+0| < |W-0| or both empty // - |W+i| = |W-i| (i = 1, ..., k) // - |W+(k+1)| > |W-(k+1)| or both empty // - W is topologically sorted // Example: // (2, 2, [(0,0), (0,1), (1,0)]) => [([],[]),([0,],[1,]),([1,],[0,]),([],[]),] // Complexity: O(N + (N + M) sqrt(N)) // Verified: https://yukicoder.me/problems/no/1615 std::vector, std::vector>> dulmage_mendelsohn(int L, int R, const std::vector> &edges) { for (auto p : edges) { assert(0 <= p.first and p.first < L); assert(0 <= p.second and p.second < R); } BipartiteMatching bm(L + R); for (auto p : edges) bm.add_edge(p.first, L + p.second); bm.solve(); DirectedGraphSCC scc(L + R); for (auto p : edges) scc.add_edge(p.first, L + p.second); for (int l = 0; l < L; ++l) { if (bm.match[l] >= L) scc.add_edge(bm.match[l], l); } int nscc = scc.FindStronglyConnectedComponents(); std::vector cmp_map(nscc, -2); std::vector vis(L + R); std::vector st; for (int c = 0; c < 2; ++c) { std::vector> to(L + R); auto color = [&L](int x) { return x >= L; }; for (auto p : edges) { int u = p.first, v = L + p.second; if (color(u) != c) std::swap(u, v); to[u].push_back(v); if (bm.match[u] == v) to[v].push_back(u); } for (int i = 0; i < L + R; ++i) { if (bm.match[i] >= 0 or color(i) != c or vis[i]) continue; vis[i] = 1, st = {i}; while (!st.empty()) { int now = st.back(); cmp_map[scc.cmp[now]] = c - 1; st.pop_back(); for (int nxt : to[now]) { if (!vis[nxt]) vis[nxt] = 1, st.push_back(nxt); } } } } int nset = 1; for (int n = 0; n < nscc; ++n) { if (cmp_map[n] == -2) cmp_map[n] = nset++; } for (auto &x : cmp_map) { if (x == -1) x = nset; } nset++; std::vector, std::vector>> groups(nset); for (int l = 0; l < L; ++l) { if (bm.match[l] < 0) continue; int c = cmp_map[scc.cmp[l]]; groups[c].first.push_back(l); groups[c].second.push_back(bm.match[l] - L); } for (int l = 0; l < L; ++l) { if (bm.match[l] >= 0) continue; int c = cmp_map[scc.cmp[l]]; groups[c].first.push_back(l); } for (int r = 0; r < R; ++r) { if (bm.match[L + r] >= 0) continue; int c = cmp_map[scc.cmp[L + r]]; groups[c].second.push_back(r); } return groups; } #line 4 "graph/test/dulmage_mendelsohn.yuki1744.test.cpp" #include #line 7 "graph/test/dulmage_mendelsohn.yuki1744.test.cpp" using namespace std; int main() { cin.tie(nullptr), ios::sync_with_stdio(false); int N, M, L; cin >> N >> M >> L; vector> edges(L); for (auto &[s, t] : edges) { cin >> s >> t; --s, --t; } auto dm = dulmage_mendelsohn(N, M, edges); set> fixed; for (auto [us, vs] : dm) { if (us.size() == 1 and vs.size() == 1) fixed.emplace(us[0], vs[0]); } for (auto [s, t] : edges) cout << (fixed.count(make_pair(s, t)) ? "No" : "Yes") << '\n'; }