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/*============================================================================
CMake - Cross Platform Makefile Generator
Copyright 2000-2009 Kitware, Inc., Insight Software Consortium
Distributed under the OSI-approved BSD License (the "License");
see accompanying file Copyright.txt for details.
This software is distributed WITHOUT ANY WARRANTY; without even the
implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the License for more information.
============================================================================*/
#ifndef cmComputeComponentGraph_h
#define cmComputeComponentGraph_h
#include "cmStandardIncludes.h"
#include "cmGraphAdjacencyList.h"
#include <stack>
/** \class cmComputeComponentGraph
* \brief Analyze a graph to determine strongly connected components.
*
* Convert a directed graph into a directed acyclic graph whose nodes
* correspond to strongly connected components of the original graph.
*
* We use Tarjan's algorithm to enumerate the components efficiently.
* An advantage of this approach is that the components are identified
* in a topologically sorted order.
*/
class cmComputeComponentGraph
{
public:
// Represent the graph with an adjacency list.
typedef cmGraphNodeList NodeList;
typedef cmGraphEdgeList EdgeList;
typedef cmGraphAdjacencyList Graph;
cmComputeComponentGraph(Graph const& input);
~cmComputeComponentGraph();
/** Get the adjacency list of the component graph. */
Graph const& GetComponentGraph() const
{ return this->ComponentGraph; }
EdgeList const& GetComponentGraphEdges(int c) const
{ return this->ComponentGraph[c]; }
/** Get map from component index to original node indices. */
std::vector<NodeList> const& GetComponents() const
{ return this->Components; }
NodeList const& GetComponent(int c) const
{ return this->Components[c]; }
/** Get map from original node index to component index. */
std::vector<int> const& GetComponentMap() const
{ return this->TarjanComponents; }
private:
void TransferEdges();
Graph const& InputGraph;
Graph ComponentGraph;
// Tarjan's algorithm.
struct TarjanEntry
{
int Root;
int VisitIndex;
};
int TarjanWalkId;
std::vector<int> TarjanVisited;
std::vector<int> TarjanComponents;
std::vector<TarjanEntry> TarjanEntries;
std::stack<int> TarjanStack;
int TarjanIndex;
void Tarjan();
void TarjanVisit(int i);
// Connected components.
std::vector<NodeList> Components;
};
#endif
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