<HTML>
<!--
     Copyright (c) Jeremy Siek 2000
    
     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)
  -->
<Head>
<Title>Boost Graph Library: Adjacency Matrix</Title>
<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" 
        ALINK="#ff0000"> 
<IMG SRC="../../../boost.png" 
     ALT="C++ Boost" width="277" height="86"> 

<BR Clear>

<H1><A NAME="sec:adjacency-matrix-class"></A>
<pre>
adjacency_matrix&lt;Directed, VertexProperty, 
                 EdgeProperty, GraphProperty,
                 Allocator&gt;
</pre>
</H1>

The <tt>adjacency_matrix</tt> class implements the BGL graph interface
using the traditional adjacency matrix storage format. For a graph
with <i>V</i> vertices, a <i>V x V</i> matrix is used, where each
element <i>a<sub>ij</sub></i> is a boolean flag that says whether
there is an edge from vertex <i>i</i> to vertex <i>j</i>. <a
href="#fig:adj-matrix-graph">Figure 1</a> shows the adjacency matrix
representation of a graph.

<P></P>
<DIV ALIGN="center"><A NAME="fig:adj-matrix-graph"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 1:</STRONG> Adjacency Matrix Representation of a Directed Graph.</CAPTION>
<TR><TD><IMG SRC="./figs/adj-matrix-graph3.gif" width="386" height="284"></TD>
<TD><IMG SRC="./figs/adj-matrix.gif" width="135" height="136"></TD></TR>
</TABLE>
</DIV><P></P>

The advantage of this matrix format over the adjacency list is that
edge insertion and removal is constant time.  There are several
disadvantages. The first is that the amount of memory used is
<i>O(V<sup>2</sup>)</i> instead of <i>O(V + E)</i> (where <i>E</i> is
the number of edges). The second is that operations that traverse all
the out-edges of each vertex (such as breadth-first search) run in
<i>O(V<sup>2</sup>)</i> time instead of <i>O(V + E)</i> time for the
adjacency list. In short, it is better to use the
<tt>adjacency_matrix</tt> for dense graphs (where <i>E</i> is close to
<i>V<sup>2</sup></i>) and it is better to use <a
href="adjacency_list.html"><tt>adjacency_list</tt></a> for sparse
graphs (where <i>E</i> is much smaller than <i>V<sup>2</sup></i>).

The <tt>adjacency_matrix</tt> class extends the traditional
data-structure by allowing objects to be attached to vertices and
edges using the same property template parameters supported by <a
href="adjacency_list.html"><tt>adjacency_list</tt></a>. These may be
<a href="bundles.html">bundled properties</a> or standard (backward-compatible)
<a
href="using_adjacency_list.html#sec:adjacency-list-properties">interior
properties</a>. The types of all property values must be
Copy Constructible, Assignable and Default Constructible. 

In the case of an undirected graph, the
<tt>adjacency_matrix</tt>. class does not use a full <i>V x V</i>
matrix but instead uses a lower triangle (the diagonal and below)
since the matrix for an undirected graph is symmetric. This reduces
the storage to <i>(V<sup>2</sup>)/2</i>.  <a
href="#fig:undir-adj-matrix-graph">Figure 2</a> shows an adjacency
matrix representation of an undirected graph.

<P></P>
<DIV ALIGN="center"><A NAME="fig:undir-adj-matrix-graph"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 1:</STRONG> Adjacency Matrix Representation of an Undirected Graph.</CAPTION>
<TR><TD><IMG SRC="./figs/undir-adj-matrix-graph3.gif" width="260" height="240"></TD>
<TD><IMG SRC="./figs/undir-adj-matrix2.gif" width="135" height="136"></TD></TR>
</TABLE>
</DIV><P></P>


<h3>Example</h3>

Creating the graph of <a href="#fig:adj-matrix-graph">Figure 1</a>. 
<pre>
  enum { A, B, C, D, E, F, N };
  const char* name = "ABCDEF";
  
  typedef boost::adjacency_matrix&lt;boost::directedS> Graph;
  Graph g(N);
  add_edge(B, C, g);
  add_edge(B, F, g);
  add_edge(C, A, g);
  add_edge(C, C, g);
  add_edge(D, E, g);
  add_edge(E, D, g);
  add_edge(F, A, g);

  std::cout &lt;&lt; "vertex set: ";
  boost::print_vertices(g, name);
  std::cout &lt;&lt; std::endl;

  std::cout &lt;&lt; "edge set: ";
  boost::print_edges(g, name);
  std::cout &lt;&lt; std::endl;

  std::cout &lt;&lt; "out-edges: " &lt;&lt; std::endl;
  boost::print_graph(g, name);
  std::cout &lt;&lt; std::endl;
</pre>
The output is:
<pre>
  vertex set: A B C D E F 

  edge set: (B,C) (B,F) (C,A) (C,C) (D,E) (E,D) (F,A) 

  out-edges: 
  A --> 
  B --> C F 
  C --> A C 
  D --> E 
  E --> D 
  F --> A 
</pre>

Creating the graph of <a href="#fig:undir-adj-matrix-graph">Figure 2</a>.
<pre>
  enum { A, B, C, D, E, F, N };
  const char* name = "ABCDEF";

  typedef boost::adjacency_matrix&lt;boost::undirectedS> UGraph;
  UGraph ug(N);
  add_edge(B, C, ug);
  add_edge(B, F, ug);
  add_edge(C, A, ug);
  add_edge(D, E, ug);
  add_edge(F, A, ug);

  std::cout &lt;&lt; "vertex set: ";
  boost::print_vertices(ug, name);
  std::cout &lt;&lt; std::endl;

  std::cout &lt;&lt; "edge set: ";
  boost::print_edges(ug, name);
  std::cout &lt;&lt; std::endl;

  std::cout &lt;&lt; "incident edges: " &lt;&lt; std::endl;
  boost::print_graph(ug, name);
  std::cout &lt;&lt; std::endl;
</pre>
The output is:
<pre>
  vertex set: A B C D E F 

  edge set: (C,A) (C,B) (E,D) (F,A) (F,B) 

  incident edges: 
  A &lt;--> C F 
  B &lt;--> C F 
  C &lt;--> A B 
  D &lt;--> E 
  E &lt;--> D 
  F &lt;--> A B 
</pre>


<h3>Where Defined</h3>

<a href="../../../boost/graph/adjacency_matrix.hpp"><tt>boost/graph/adjacency_matrix.hpp</tt></a>


<h3>Template Parameters</h3>

<p>
<table border>

<TR>
<th>Parameter</th><th>Description</th><th>Default</th>
</tr>

<tr>
  <td><tt>Directed</tt></td>
  <td>A selector to choose whether the graph is directed or undirected. The options are <tt>directedS</tt> and <tt>undirectedS</tt>.</td>
  <td><tt>directedS</tt></td>
</tr>
<tr>
  <td><tt>VertexProperty</tt></td>
  <td>for specifying internal property storage.</td>
  <td><tt>no_property</tt></td>
</tr>
<tr>
  <td><tt>EdgeProperty</tt></td>
  <td>for specifying internal property storage.</td>
  <td><tt>no_property</tt></td>
</tr>
<tr>
  <td><tt>GraphProperty</tt></td>
  <td>for specifying property storage for the graph object.</td>
  <td><tt>no_property</tt></td>
</tr>

</table>

<h3>Model Of</h3>

<a href="./VertexAndEdgeListGraph.html">VertexAndEdgeListGraph</a>, 
<a href="./IncidenceGraph.html">Incidence Graph</a>,
<a href="./BidirectionalGraph.html">Bidirectional Graph</a>,
<a
href="./AdjacencyMatrix.html">AdjacencyMatrix</a>, <a
href="./MutablePropertyGraph.html">MutablePropertyGraph</a>,
<a href="../../utility/CopyConstructible.html">CopyConstructible</a>,
and <a href="../../utility/Assignable.html">Assignable</a>.


<h3>Associated Types</h3>

<hr>

<tt>graph_traits&lt;adjacency_matrix&gt;::vertex_descriptor</tt>
<br><br>
The type for the vertex descriptors associated with the
<tt>adjacency_matrix</tt>.<br>
(Required by <a href="./Graph.html">Graph</a>.)

<hr>

<tt>graph_traits&lt;adjacency_matrix&gt;::edge_descriptor</tt>
<br><br>
The type for the edge descriptors associated with the
  <tt>adjacency_matrix</tt>.<br>
 (Required by <a href="Graph.html">Graph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::vertex_iterator</tt>
<br><br>
  The type for the iterators returned by <tt>vertices()</tt>.  
  The vertex iterator models <a href="http://www.sgi.com/tech/stl/RandomAccessIterator.html">RandomAccessIterator</a>. <br>
 (Required by <a href="VertexListGraph.html">VertexListGraph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::edge_iterator</tt>
<br><br>
  The type for the iterators returned by <tt>edges()</tt>. This
  iterator models <a href="../../utility/MultiPassInputIterator.html">MultiPassInputIterator</a>.<br>
 (Required by <a href="EdgeListGraph.html">EdgeListGraph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::out_edge_iterator</tt>
<br><br>
  The type for the iterators returned by <tt>out_edges()</tt>.  This
  iterator models <a href="../../utility/MultiPassInputIterator.html">MultiPassInputIterator</a>. <br>
  (Required by <a href="IncidenceGraph.html">IncidenceGraph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::in_edge_iterator</tt>
<br><br>
  The type for the iterators returned by <tt>in_edges()</tt>.  This
  iterator models <a href="../../utility/MultiPassInputIterator.html">MultiPassInputIterator</a>. <br>
  (Required by <a href="BidirectionalGraph.html">BidirectionalGraph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::adjacency_iterator</tt>
<br><br>
  The type for the iterators returned by <tt>adjacent_vertices()</tt>. This
  iterator models the same concept as the out-edge iterator.<br>
  (Required by <a href="AdjacencyGraph.html">AdjacencyGraph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::directed_category</tt>
<br><br>
  Provides information about whether the graph is directed
  (<tt>directed_tag</tt>) or undirected (<tt>undirected_tag</tt>).<br>
  (Required by <a href="Graph.html">Graph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::edge_parallel_category</tt>
<br><br>
  An adjacency matrix does not allow the insertion of
  parallel edges, so this type is always
  <tt>disallow_parallel_edge_tag</tt>. <br>
  (Required by <a href="Graph.html">Graph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::vertices_size_type</tt>
<br><br>
  The type used for dealing with the number of vertices in
  the graph.<br>
  (Required by <a href="VertexListGraph.html">VertexListGraph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::edges_size_type</tt>
<br><br>
  The type used for dealing with the number of edges in the graph.<br>
  (Required by <a href="EdgeListGraph.html">EdgeListGraph</a>.)

<hr>
<tt>graph_traits&lt;adjacency_matrix&gt;::degree_size_type</tt>
<br><br>
  The type used for dealing with the number of out-edges of a vertex.<br>
  (Required by <a href="IncidenceGraph.html">IncidenceGraph</a>.)

<hr>
<tt>property_map&lt;adjacency_matrix, PropertyTag&gt;::type</tt><br>
<tt>property_map&lt;adjacency_matrix, PropertyTag&gt;::const_type</tt>
<br><br>
  The map type for vertex or edge properties in the graph. The
  specific property is specified by the <tt>PropertyTag</tt> template
  argument, and must match one of the properties specified in the
  <tt>VertexProperty</tt> or <tt>EdgeProperty</tt> for the graph.<br>
  (Required by <a href="PropertyGraph.html">PropertyGraph</a>.)

<hr>

<h3>Member Functions</h3>

<hr>
<pre>
adjacency_matrix(vertices_size_type n,
                 const GraphProperty& p = GraphProperty())
</pre>
Creates a graph object with <tt>n</tt> vertices and zero edges.<br>
(Required by <a href="MutableGraph.html">MutableGraph</a>.)

<hr>
<pre>
template &lt;typename EdgeIterator&gt;
adjacency_matrix(EdgeIterator first,
                 EdgeIterator last,
                 vertices_size_type n,
                 const GraphProperty& p = GraphProperty())
</pre>
  Creates a graph object with <tt>n</tt> vertices with the edges
  specified in the edge list given by the range <tt>[first, last)</tt>.
  The value type of the <tt>EdgeIterator</tt> must be a
  <tt>std::pair</tt>, where the type in the pair is an integer type. The
  integers will correspond to vertices, and they must all fall in the
  range of
  <tt>[0, n)</tt>. <br>
  (Required by <a href="IteratorConstructibleGraph.html">IteratorConstructibleGraph</a>.)

<hr>
<pre>
template &lt;typename EdgeIterator, typename EdgePropertyIterator&gt;
adjacency_matrix(EdgeIterator first, EdgeIterator last,
                 EdgePropertyIterator ep_iter,
                 vertices_size_type n,
                 const GraphProperty& p = GraphProperty())
</pre>
  Creates a graph object with <tt>n</tt> vertices, with the edges
  specified in the edge list given by the range <tt>[first, last)</tt>.
  The value type of the <tt>EdgeIterator</tt> must be a
  <tt>std::pair</tt>, where the type in the pair is an integer type. The
  integers will correspond to vertices, and they must all fall in the
  range of <tt>[0, n)</tt>. The <tt>value_type</tt> of the
  <tt>ep_iter</tt> should be <tt>EdgeProperty</tt>.

<hr>


<h3>Non-Member Functions</h3>

<hr>
<pre>
std::pair&lt;vertex_iterator, vertex_iterator&gt;
vertices(const adjacency_matrix&amp; g)
</pre>
Returns an iterator-range providing access to the vertex set of graph <tt>g</tt>.<br>
(Required by <a href="VertexListGraph.html">VertexListGraph</a>.)

<hr>
<pre>
std::pair&lt;edge_iterator, edge_iterator&gt;
edges(const adjacency_matrix&amp; g);
</pre>
Returns an iterator-range providing access to the edge set of graph <tt>g</tt>.<br>
(Required by <a href="EdgeListGraph.html">EdgeListGraph</a>.)

<hr>
<pre>
std::pair&lt;adjacency_iterator, adjacency_iterator&gt;
adjacent_vertices(vertex_descriptor v, const adjacency_matrix&amp; g)
</pre>
Returns an iterator-range providing access to the vertices adjacent to
vertex <tt>v</tt> in graph <tt>g</tt>.<br>
(Required by <a href="AdjacencyGraph.html">AdjacencyGraph</a>.)

<hr>
<pre>
std::pair&lt;out_edge_iterator, out_edge_iterator&gt;
out_edges(vertex_descriptor v, const adjacency_matrix&amp; g)
</pre>
Returns an iterator-range providing access to the out-edges of
vertex <tt>v</tt> in graph <tt>g</tt>. If the graph is undirected,
this iterator-range provides access to all edges incident on
vertex <tt>v</tt>. <br>
(Required by <a href="IncidenceGraph.html">IncidenceGraph</a>.)

<hr>
<pre>
vertex_descriptor
source(edge_descriptor e, const adjacency_matrix&amp; g)
</pre>
Returns the source vertex of edge <tt>e</tt>.<br>
(Required by <a href="IncidenceGraph.html">IncidenceGraph</a>.)

<hr>
<pre>
vertex_descriptor
target(edge_descriptor e, const adjacency_matrix&amp; g)
</pre>
Returns the target vertex of edge <tt>e</tt>.<br>
(Required by <a href="IncidenceGraph.html">IncidenceGraph</a>.)

<hr>
<pre>
degree_size_type
out_degree(vertex_descriptor u, const adjacency_matrix&amp; g)
</pre>
Returns the number of edges leaving vertex <tt>u</tt>.<br>
(Required by <a href="IncidenceGraph.html">IncidenceGraph</a>.) 
<hr>

<hr>
<pre>
std::pair&lt;in_edge_iterator, in_edge_iterator&gt;
in_edges(vertex_descriptor v, const adjacency_matrix&amp; g)
</pre>
Returns an iterator-range providing access to the in-edges of
vertex <tt>v</tt> in graph <tt>g</tt>. If the graph is undirected,
this iterator-range provides access to all edges incident on
vertex <tt>v</tt>. <br>
(Required by <a href="BidirectionalGraph.html">BidirectionalGraph</a>.)

<hr>
<pre>
degree_size_type
in_degree(vertex_descriptor u, const adjacency_matrix&amp; g)
</pre>
Returns the number of edges entering vertex <tt>u</tt>.<br>
(Required by <a href="BidirectionalGraph.html">BidirectionalGraph</a>.) 
<hr>

<hr>
<pre>
vertices_size_type num_vertices(const adjacency_matrix&amp; g)
</pre>
Returns the number of vertices in the graph <tt>g</tt>.<br>
(Required by <a href="VertexListGraph.html">VertexListGraph</a>.)

<hr>
<pre>
edges_size_type num_edges(const adjacency_matrix&amp; g)
</pre>
Returns the number of edges in the graph <tt>g</tt>.<br>
(Required by <a href="EdgeListGraph.html">EdgeListGraph</a>.)

<hr>
<pre>
vertex_descriptor vertex(vertices_size_type n, const adjacency_matrix&amp; g)
</pre>
Returns the nth vertex in the graph's vertex list.

<hr>
<pre>
std::pair&lt;edge_descriptor, bool&gt;
edge(vertex_descriptor u, vertex_descriptor v,
     const adjacency_matrix&amp; g)
</pre>
Returns the edge connecting vertex <tt>u</tt> to vertex <tt>v</tt> in graph <tt>g</tt>.<br>
(Required by <a href="AdjacencyMatrix.html">AdjacencyMatrix</a>.)

<hr>
<pre>
std::pair&lt;edge_descriptor, bool&gt;
add_edge(vertex_descriptor u, vertex_descriptor v,
         adjacency_matrix&amp; g)
</pre>
  Adds edge <tt>(u,v)</tt> to the graph and returns the edge descriptor for
  the new edge. If the edge is already in the graph then a duplicate
  will not be added and the <tt>bool</tt> flag will be <tt>false</tt>.
  This operation does not invalidate any of the graph's iterators
  or descriptors.<br>
(Required by <a href="MutableGraph.html">MutableGraph</a>.)

<hr>
<pre>
std::pair&lt;edge_descriptor, bool&gt;
add_edge(vertex_descriptor u, vertex_descriptor v,
         const EdgeProperty& p,
         adjacency_matrix&amp; g)
</pre>
Adds edge <tt>(u,v)</tt> to the graph and attaches <tt>p</tt> as the
value of the edge's internal property storage.  Also see the previous
<tt>add_edge()</tt> member function for more details.

<hr>
<pre>
void remove_edge(vertex_descriptor u, vertex_descriptor v,
                 adjacency_matrix&amp; g)
</pre>
Removes the edge <tt>(u,v)</tt> from the graph.  <br>
(Required by <a href="MutableGraph.html">MutableGraph</a>.)

<hr>
<pre>
void remove_edge(edge_descriptor e, adjacency_matrix&amp; g)
</pre>
Removes the edge <tt>e</tt> from the graph. This is equivalent
to calling <tt>remove_edge(source(e, g), target(e, g), g)</tt>.<br>
(Required by <a href="MutableGraph.html">MutableGraph</a>.)

<hr>
<pre>
void clear_vertex(vertex_descriptor u, adjacency_matrix&amp; g)
</pre>
Removes all edges to and from vertex <tt>u</tt>. The vertex still appears
in the vertex set of the graph.<br>
(Required by <a href="MutableGraph.html">MutableGraph</a>.)

<hr>
<pre>
template &lt;typename Property&gt;
property_map&lt;adjacency_matrix, Property&gt;::type
get(Property, adjacency_matrix&amp; g)

template &lt;typename Property&gt;
property_map&lt;adjacency_matrix, Property&gt;::const_type
get(Property, const adjacency_matrix&amp; g)
</pre>
Returns the property map object for the vertex property specified by
<tt>Property</tt>. The <tt>Property</tt> must match one of the
properties specified in the graph's <tt>VertexProperty</tt> template
argument.<br>
(Required by <a href="PropertyGraph.html">PropertyGraph</a>.)

<hr>
<pre>
template &lt;typename Property, typename X&gt;
typename property_traits&lt;
  typename property_map&lt;adjacency_matrix, Property&gt;::const_type
&gt;::value_type
get(Property, const adjacency_matrix&amp; g, X x)
</pre>
This returns the property value for <tt>x</tt>, which is either
a vertex or edge descriptor.<br>
(Required by <a href="PropertyGraph.html">PropertyGraph</a>.)

<hr>
<pre>
template &lt;typename Property, typename X, typename Value&gt;
void
put(Property, const adjacency_matrix&amp; g, X x, const Value& value)
</pre>
This sets the property value for <tt>x</tt> to
<tt>value</tt>. <tt>x</tt> is either a vertex or edge descriptor.
<tt>Value</tt> must be convertible to
<tt>typename property_traits&lt;property_map&lt;adjacency_matrix, Property&gt;::type&gt;::value_type</tt>.<br>
(Required by <a href="PropertyGraph.html">PropertyGraph</a>.)

<hr>
<pre>
template &lt;typename GraphProperty, typename GraphProperty&gt;
typename property_value&lt;GraphProperty, GraphProperty&gt;::type&amp;
get_property(adjacency_matrix&amp; g, GraphProperty)
</pre>
Return the property specified by <tt>GraphProperty</tt> that is attached
to the graph object <tt>g</tt>. The <tt>property_value</tt> traits class
is defined in <tt>boost/pending/property.hpp</tt>.

<hr>
<pre>
template &lt;typename GraphProperty, typename GraphProperty&gt;
const typename property_value&lt;GraphProperty, GraphProperty&gt;::type&amp;
get_property(const adjacency_matrix&amp; g, GraphProperty)
</pre>
Return the property specified by <tt>GraphProperty</tt> that is
attached to the graph object <tt>g</tt>.  The <tt>property_value</tt>
traits class is defined in <tt>boost/pending/property.hpp</tt>.


<hr>