From fa461fe18a0b0663a65e67f3dc7b183c09dd65e1 Mon Sep 17 00:00:00 2001
From: Jeremy Siek <jeremy.siek@gmail.com>
Date: Sat, 24 Feb 2001 07:31:37 +0000
Subject: [PATCH] new file

[SVN r9320]
---
 example/strongly_connected_components.cpp | 57 ++++++++++++++++
 include/boost/graph/tarjan_scc.hpp        | 79 +++++++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 example/strongly_connected_components.cpp
 create mode 100644 include/boost/graph/tarjan_scc.hpp

diff --git a/example/strongly_connected_components.cpp b/example/strongly_connected_components.cpp
new file mode 100644
index 00000000..9a9068af
--- /dev/null
+++ b/example/strongly_connected_components.cpp
@@ -0,0 +1,57 @@
+//=======================================================================
+// Copyright 1997-2001 University of Notre Dame.
+// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
+//
+// This file is part of the Boost Graph Library
+//
+// You should have received a copy of the License Agreement for the
+// Boost Graph Library along with the software; see the file LICENSE.
+// If not, contact Office of Research, University of Notre Dame, Notre
+// Dame, IN 46556.
+//
+// Permission to modify the code and to distribute modified code is
+// granted, provided the text of this NOTICE is retained, a notice that
+// the code was modified is included with the above COPYRIGHT NOTICE and
+// with the COPYRIGHT NOTICE in the LICENSE file, and that the LICENSE
+// file is distributed with the modified code.
+//
+// LICENSOR MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.
+// By way of example, but not limitation, Licensor MAKES NO
+// REPRESENTATIONS OR WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY
+// PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE COMPONENTS
+// OR DOCUMENTATION WILL NOT INFRINGE ANY PATENTS, COPYRIGHTS, TRADEMARKS
+// OR OTHER RIGHTS.
+//=======================================================================
+
+#include <vector>
+#include <boost/graph/tarjan_scc.hpp>
+#include <boost/graph/adjacency_list.hpp>
+#include <boost/graph/graphviz.hpp>
+#include <boost/graph/graph_utility.hpp>
+
+int main(int, char*[])
+{
+  using namespace boost;
+  const char* name = "abcdefghij";
+
+  GraphvizGraph G;
+  read_graphviz("scc2.dot", G);
+
+  typedef graph_traits<GraphvizGraph>::vertex_descriptor Vertex;
+    
+  std::vector<int> comp(num_vertices(G)), dfs_numbers(num_vertices(G));
+  std::vector<default_color_type> color(num_vertices(G));
+  std::vector<Vertex> root(num_vertices(G));
+  int num = tarjan_scc(G, &comp[0], &root[0], &color[0], &dfs_numbers[0]);
+    
+  cout << "A directed graph:" << endl;
+  print_graph(G, name);
+  cout << endl;
+  cout << "Total number of components: " << num << endl;
+  std::vector<int>::iterator i;
+  for (i = comp.begin(); i != comp.end(); ++i)
+    cout << "Vertex " << name[i - comp.begin()]
+	 <<" is in component " << *i << endl;
+    
+  return 0;
+}
diff --git a/include/boost/graph/tarjan_scc.hpp b/include/boost/graph/tarjan_scc.hpp
new file mode 100644
index 00000000..17672efe
--- /dev/null
+++ b/include/boost/graph/tarjan_scc.hpp
@@ -0,0 +1,79 @@
+#ifndef BOOST_TARJAN_SCC_HPP
+#define BOOST_TARJAN_SCC_HPP
+
+#include <boost/graph/depth_first_search.hpp>
+
+namespace boost {
+
+  namespace detail {
+  
+    template <typename ComponentMap, typename RootMap, typename DFSNumberMap,
+              typename Stack>
+    class tarjan_scc_visitor : public dfs_visitor<> {
+      typedef typename property_traits<ComponentMap>::value_type comp_type;
+      typedef typename property_traits<DFSNumberMap>::value_type time_type;
+    public:
+      tarjan_scc_visitor(ComponentMap comp_map, RootMap r, DFSNumberMap n, 
+			 comp_type& c_, Stack& s_)
+	: c(c_), comp(comp_map), root(r), dfs_number(n),
+	  dfs_time(time_type()), s(s_) { }
+
+      template <typename Vertex, typename Graph>
+      void discover_vertex(Vertex v, Graph& ) {
+	root[v] = v;
+	comp[v] = std::numeric_limits<comp_type>::max();
+	dfs_number[v] = dfs_time++;
+	s.push(v);
+      }
+      template <typename Vertex, typename Graph>
+      void finish_vertex(Vertex v, Graph& g) {
+	Vertex w;
+	typename graph_traits<Graph>::out_edge_iterator ei, ei_end;
+	for (tie(ei, ei_end) = out_edges(v, g); ei != ei_end; ++ei) {
+	  w = target(*ei, g);
+	  if (comp[w] == std::numeric_limits<comp_type>::max())
+	    root[v] = this->min_dfs_number(root[v], root[w]);
+	}
+	if (root[v] == v) {
+	  do {
+	    w = s.top(); s.pop();
+	    comp[w] = c;
+	  } while (w != v);
+	  ++c;
+	}
+      }
+    private:
+      template <typename Vertex>
+      Vertex min_dfs_number(Vertex u, Vertex v) {
+	return dfs_number[u] < dfs_number[v] ? u : v;
+      }
+
+      comp_type& c;
+      ComponentMap comp;
+      RootMap root;
+      DFSNumberMap dfs_number;
+      time_type dfs_time;
+      Stack& s;
+    };
+
+  } // namespace detail 
+
+  template <typename Graph, typename ComponentMap, typename RootMap,
+            typename ColorMap, typename DFSNumberMap>
+  typename property_traits<ComponentMap>::value_type
+  tarjan_scc(Graph& g,          // Input
+	     ComponentMap comp, // Output
+	     // Internal record keeping
+	     RootMap root, ColorMap color, DFSNumberMap dfs_number_map)
+  {
+    typename property_traits<ComponentMap>::value_type total = 0;
+    typedef std::stack<typename graph_traits<Graph>::vertex_descriptor> Stack;
+    Stack s;
+    detail::tarjan_scc_visitor<ComponentMap, RootMap, DFSNumberMap, Stack> 
+      vis(comp, root, dfs_number_map, total, s);
+    depth_first_search(g, vis, color);
+    return total;
+  }
+} // namespace boost
+
+#endif // BOOST_TARJAN_SCC_HPP