comparison DEPENDENCIES/generic/include/boost/graph/incremental_components.hpp @ 16:2665513ce2d3

Add boost headers

+//
+//=======================================================================
+// Copyright 1997-2001 University of Notre Dame.
+// Copyright 2009 Trustees of Indiana University.
+// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek, Michael Hansen
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//=======================================================================
+//
+
+#ifndef BOOST_INCREMENTAL_COMPONENTS_HPP
+#define BOOST_INCREMENTAL_COMPONENTS_HPP
+
+#include <boost/detail/iterator.hpp>
+#include <boost/graph/detail/incremental_components.hpp>
+#include <boost/iterator/counting_iterator.hpp>
+#include <boost/make_shared.hpp>
+#include <boost/pending/disjoint_sets.hpp>
+#include <iterator>
+
+namespace boost {
+
+  // A connected component algorithm for the case when dynamically
+  // adding (but not removing) edges is common.  The
+  // incremental_components() function is a preparing operation. Call
+  // same_component to check whether two vertices are in the same
+  // component, or use disjoint_set::find_set to determine the
+  // representative for a vertex.
+
+  // This version of connected components does not require a full
+  // Graph. Instead, it just needs an edge list, where the vertices of
+  // each edge need to be of integer type. The edges are assumed to
+  // be undirected. The other difference is that the result is stored in
+  // a container, instead of just a decorator.  The container should be
+  // empty before the algorithm is called. It will grow during the
+  // course of the algorithm. The container must be a model of
+  // BackInsertionSequence and RandomAccessContainer
+  // (std::vector is a good choice). After running the algorithm the
+  // index container will map each vertex to the representative
+  // vertex of the component to which it belongs.
+  //
+  // Adapted from an implementation by Alex Stepanov. The disjoint
+  // sets data structure is from Tarjan's "Data Structures and Network
+  // Algorithms", and the application to connected components is
+  // similar to the algorithm described in Ch. 22 of "Intro to
+  // Algorithms" by Cormen, et. all.
+  //  
+
+  // An implementation of disjoint sets can be found in
+  // boost/pending/disjoint_sets.hpp
+  
+  template <class EdgeListGraph, class DisjointSets>
+  void incremental_components(EdgeListGraph& g, DisjointSets& ds)
+  {
+    typename graph_traits<EdgeListGraph>::edge_iterator e, end;
+    for (boost::tie(e,end) = edges(g); e != end; ++e)
+      ds.union_set(source(*e,g),target(*e,g));
+  }
+  
+  template <class ParentIterator>
+  void compress_components(ParentIterator first, ParentIterator last)
+  {
+    for (ParentIterator current = first; current != last; ++current) 
+      detail::find_representative_with_full_compression(first, current-first);
+  }
+  
+  template <class ParentIterator>
+  typename boost::detail::iterator_traits<ParentIterator>::difference_type
+  component_count(ParentIterator first, ParentIterator last)
+  {
+    std::ptrdiff_t count = 0;
+    for (ParentIterator current = first; current != last; ++current) 
+      if (*current == current - first) ++count; 
+    return count;
+  }
+  
+  // This algorithm can be applied to the result container of the
+  // connected_components algorithm to normalize
+  // the components.
+  template <class ParentIterator>
+  void normalize_components(ParentIterator first, ParentIterator last)
+  {
+    for (ParentIterator current = first; current != last; ++current) 
+      detail::normalize_node(first, current - first);
+  }
+  
+  template <class VertexListGraph, class DisjointSets> 
+  void initialize_incremental_components(VertexListGraph& G, DisjointSets& ds)
+  {
+    typename graph_traits<VertexListGraph>
+      ::vertex_iterator v, vend;
+    for (boost::tie(v, vend) = vertices(G); v != vend; ++v)
+      ds.make_set(*v);
+  }
+
+  template <class Vertex, class DisjointSet>
+  inline bool same_component(Vertex u, Vertex v, DisjointSet& ds)
+  {
+    return ds.find_set(u) == ds.find_set(v);
+  }
+
+  // Class that builds a quick-access indexed linked list that allows
+  // for fast iterating through a parent component's children.
+  template <typename IndexType>
+  class component_index {
+
+  private:
+    typedef std::vector<IndexType> IndexContainer;
+
+  public:
+    typedef counting_iterator<IndexType> iterator;
+    typedef iterator const_iterator;
+    typedef IndexType value_type;
+    typedef IndexType size_type;
+
+    typedef detail::component_index_iterator<typename IndexContainer::iterator>
+      component_iterator;
+
+  public:
+    template <typename ParentIterator,
+              typename ElementIndexMap>
+    component_index(ParentIterator parent_start,
+                    ParentIterator parent_end,
+                    const ElementIndexMap& index_map) :
+      m_num_elements(std::distance(parent_start, parent_end)),
+      m_components(make_shared<IndexContainer>()),
+      m_index_list(make_shared<IndexContainer>(m_num_elements)) {
+
+      build_index_lists(parent_start, index_map);
+      
+    } // component_index
+
+    template <typename ParentIterator>
+    component_index(ParentIterator parent_start,
+                    ParentIterator parent_end) :
+      m_num_elements(std::distance(parent_start, parent_end)),
+      m_components(make_shared<IndexContainer>()),
+      m_index_list(make_shared<IndexContainer>(m_num_elements)) {
+
+      build_index_lists(parent_start, boost::identity_property_map());
+
+    } // component_index
+
+    // Returns the number of components
+    inline std::size_t size() const {
+      return (m_components->size());
+    }
+
+    // Beginning iterator for component indices
+    iterator begin() const {
+      return (iterator(0));
+    }
+
+    // End iterator for component indices
+    iterator end() const {
+      return (iterator(this->size()));
+    }
+
+    // Returns a pair of begin and end iterators for the child
+    // elements of component [component_index].
+    std::pair<component_iterator, component_iterator>
+    operator[](IndexType component_index) const {
+
+      IndexType first_index = (*m_components)[component_index];
+
+      return (std::make_pair
+              (component_iterator(m_index_list->begin(), first_index),
+               component_iterator(m_num_elements)));
+    }
+
+  private:
+    template <typename ParentIterator,
+              typename ElementIndexMap>
+    void build_index_lists(ParentIterator parent_start,
+                           const ElementIndexMap& index_map) {
+
+      typedef typename std::iterator_traits<ParentIterator>::value_type Element;
+      typename IndexContainer::iterator index_list =
+        m_index_list->begin();
+
+      // First pass - find root elements, construct index list
+      for (IndexType element_index = 0; element_index < m_num_elements;
+           ++element_index) {
+
+        Element parent_element = parent_start[element_index];
+        IndexType parent_index = get(index_map, parent_element);
+
+        if (element_index != parent_index) {
+          index_list[element_index] = parent_index;
+        }
+        else {
+          m_components->push_back(element_index);
+
+          // m_num_elements is the linked list terminator
+          index_list[element_index] = m_num_elements;
+        }
+      }
+
+      // Second pass - build linked list
+      for (IndexType element_index = 0; element_index < m_num_elements;
+           ++element_index) {
+
+        Element parent_element = parent_start[element_index];
+        IndexType parent_index = get(index_map, parent_element);
+
+        if (element_index != parent_index) {
+
+          // Follow list until a component parent is found
+          while (index_list[parent_index] != m_num_elements) {
+            parent_index = index_list[parent_index];
+          }
+
+          // Push element to the front of the linked list
+          index_list[element_index] = index_list[parent_index];
+          index_list[parent_index] = element_index;
+        }
+      }
+
+    } // build_index_lists
+
+  protected:
+    IndexType m_num_elements;
+    shared_ptr<IndexContainer> m_components, m_index_list;
+
+  }; // class component_index
+ 
+} // namespace boost
+
+#endif // BOOST_INCREMENTAL_COMPONENTS_HPP