74 lines
1.4 KiB
C++
74 lines
1.4 KiB
C++
#ifndef TARJAN_H_
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#define TARJAN_H_
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#include "graph/graph.h"
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using namespace graph;
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#include <stack>
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#include <iostream>
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#include <ranges>
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#include <iterator>
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#include <algorithm>
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namespace algorithm {
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template<typename T>
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class Tarjan {
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public:
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Tarjan(Graph<T> G) : G(G) {}
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void findSCC();
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void strongConnect(Vertex<T>& v);
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std::uint16_t index = 0;
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std::stack<Vertex<T>> S;
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private:
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Graph<T> G;
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};
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template<typename T>
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void Tarjan<T>::strongConnect(Vertex<T>& v) {
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v.index, v.lowlink = index++;
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v.onStack = true;
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S.push(v);
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for (auto& w : v.edges) {
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if (w.index == -1) {
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// successor w has not yet been visited, recurse on it
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strongConnect(w);
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v.lowlink = std::min(v.lowlink, w.lowlink);
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} else if (w.onStack) {
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// successor w is in stack S and hence in the current SCC
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// if w is not on stack, then (v, w) is an edge pointing to an SCC
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// already found and must be ignored
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v.lowlink = std::min(v.lowlink, w.index);
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}
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}
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// if v is a root node, pop the stack and generate an SCC
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if (v.lowlink = v.index) {
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// start a new SCC
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Vertex<T> w;
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do {
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w = S.top();
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S.pop();
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// add w to current SCC
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} while (w != v);
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}
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}
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template<typename T>
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void Tarjan<T>::findSCC() {
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for (auto& vertex : G.vertices) {
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if (vertex.index == -1) {
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strongConnect(vertex);
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}
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}
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}
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} // namespace algorithm
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#endif |