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// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-FileCopyrightText: Copyright 2008 Sandia Corporation
// SPDX-License-Identifier: LicenseRef-BSD-3-Clause-Sandia-USGov
#include "vtkDirectedAcyclicGraph.h"
#include "vtkInformation.h"
#include "vtkInformationVector.h"
#include "vtkObjectFactory.h"
#include "vtkOutEdgeIterator.h"
#include "vtkSmartPointer.h"
#include <vector>
VTK_ABI_NAMESPACE_BEGIN
vtkStandardNewMacro(vtkDirectedAcyclicGraph);
//------------------------------------------------------------------------------
vtkDirectedAcyclicGraph::vtkDirectedAcyclicGraph() = default;
//------------------------------------------------------------------------------
vtkDirectedAcyclicGraph::~vtkDirectedAcyclicGraph() = default;
//------------------------------------------------------------------------------
vtkDirectedAcyclicGraph* vtkDirectedAcyclicGraph::GetData(vtkInformation* info)
{
return info ? vtkDirectedAcyclicGraph::SafeDownCast(info->Get(DATA_OBJECT())) : nullptr;
}
//------------------------------------------------------------------------------
vtkDirectedAcyclicGraph* vtkDirectedAcyclicGraph::GetData(vtkInformationVector* v, int i)
{
return vtkDirectedAcyclicGraph::GetData(v->GetInformationObject(i));
}
enum
{
DFS_WHITE,
DFS_GRAY,
DFS_BLACK
};
//------------------------------------------------------------------------------
static bool vtkDirectedAcyclicGraphDFSVisit(
vtkGraph* g, vtkIdType u, std::vector<int> color, vtkOutEdgeIterator* adj)
{
color[u] = DFS_GRAY;
g->GetOutEdges(u, adj);
while (adj->HasNext())
{
vtkOutEdgeType e = adj->Next();
vtkIdType v = e.Target;
if (color[v] == DFS_WHITE)
{
if (!vtkDirectedAcyclicGraphDFSVisit(g, v, color, adj))
{
return false;
}
}
else if (color[v] == DFS_GRAY)
{
return false;
}
}
return true;
}
//------------------------------------------------------------------------------
bool vtkDirectedAcyclicGraph::IsStructureValid(vtkGraph* g)
{
if (!g)
{
return false;
}
if (vtkDirectedAcyclicGraph::SafeDownCast(g))
{
return true;
}
// Empty graph is a valid DAG.
if (g->GetNumberOfVertices() == 0)
{
return true;
}
// A directed graph is acyclic iff a depth-first search of
// the graph yields no back edges.
// (from Introduction to Algorithms.
// Cormen, Leiserson, Rivest, p. 486).
vtkIdType numVerts = g->GetNumberOfVertices();
std::vector<int> color(numVerts, DFS_WHITE);
vtkSmartPointer<vtkOutEdgeIterator> adj = vtkSmartPointer<vtkOutEdgeIterator>::New();
for (vtkIdType s = 0; s < numVerts; ++s)
{
if (color[s] == DFS_WHITE)
{
if (!vtkDirectedAcyclicGraphDFSVisit(g, s, color, adj))
{
return false;
}
}
}
return true;
}
//------------------------------------------------------------------------------
void vtkDirectedAcyclicGraph::PrintSelf(ostream& os, vtkIndent indent)
{
this->Superclass::PrintSelf(os, indent);
}
VTK_ABI_NAMESPACE_END
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