101 lines
2.2 KiB
C++
101 lines
2.2 KiB
C++
#ifndef RODITTY_ZWICK_H_
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#define RODITTY_ZWICK_H_
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#include "algorithm/decremental_reachability.h"
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#include "algorithm/tarjan.h"
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#include "graph/breadth_first_tree.h"
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using namespace graph;
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namespace algo {
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template<typename T>
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class RodittyZwick : public DecrementalReachability<T> {
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public:
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RodittyZwick() = default;
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RodittyZwick(Digraph<T> G) { this->G = G; }
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//
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void init() override;
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//
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void findSCC();
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// Return true if u and v are in the same SCC
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bool query(const T& u, const T& v) override;
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// Remove edge (u,v) and update A accordingly for fast checking query
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void remove(const T& u, const T& v) override;
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void setGraph(Digraph<T> G);
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private:
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// Array used to answer strong connectivity queries in O(1) time
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std::map<T, T> A;
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// Connect each representative with its SCC
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std::map<T, SCC<T>> C;
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// Maintain in-out bfs trees
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std::map<T, BreadthFirstTree<T>> inTree;
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std::map<T, BreadthFirstTree<T>> outTree;
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};
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template<typename T>
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void RodittyZwick<T>::init() {
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findSCC();
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}
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template<typename T>
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void RodittyZwick<T>::findSCC() {
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auto SCCs = Tarjan<T>(this->G.adjMatrix).execute();
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for (auto& SCC : SCCs) {
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const auto& w = SCC.id;
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for (const auto& v : std::views::keys(SCC.adjMatrix))
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A[v] = w;
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outTree[w] = BreadthFirstTree<T>(SCC, w);
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inTree[w] = BreadthFirstTree<T>(SCC.reverse(), w);
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C[w] = SCC;
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}
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}
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template<typename T>
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bool RodittyZwick<T>::query(const T& u, const T& v) {
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return A[u] == A[v];
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}
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template<typename T>
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void RodittyZwick<T>::remove(const T& u, const T& v) {
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const auto& w = A[u];
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C[w].remove(u, v);
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this->G.remove(u, v);
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// If u and v are not in the same SCC, do nothing
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if (A[u] != A[v]) return;
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// If edge (u,v) is not contained in both inTree and outTree do nothing
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if (!inTree[w].adjMatrix[u].contains(v) &&
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!outTree[w].adjMatrix[u].contains(v))
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return;
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// Update In(w) and Out(w)
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outTree[w] = BreadthFirstTree<T>(C[w], w);
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inTree[w] = BreadthFirstTree<T>(C[w].reverse(), w);
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// If a SCC is broken, compute all SCCs again
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if (!inTree[w].adjMatrix.count(u) || !outTree[w].adjMatrix.count(v))
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findSCC();
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}
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template<typename T>
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void RodittyZwick<T>::setGraph(Digraph<T> G) {
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this->G = G;
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}
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}; // namespace algo
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#endif |