+/* Copyright (C) 2006-2008 Joris Mooij [j dot mooij at science dot ru dot nl]
+ Radboud University Nijmegen, The Netherlands
+
+ This file is part of libDAI.
+
+ libDAI is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ libDAI is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with libDAI; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+
+#include <dai/bipgraph.h>
+
+
+namespace dai {
+
+
+using namespace std;
+
+
+/// Remove node of type 1 and all incident edges.
+void BipartiteGraph::erase1( size_t n1 ) {
+ assert( n1 < nr1() );
+ // Erase neighbor entry of node n1
+ _nb1.erase( _nb1.begin() + n1 );
+ // Adjust neighbor entries of nodes of type 2
+ for( size_t n2 = 0; n2 < nr2(); n2++ ) {
+ for( size_t iter = 0; iter < nb2(n2).size(); ) {
+ Neighbor &m1 = nb2(n2, iter);
+ if( m1.node == n1 ) {
+ // delete this entry, because it points to the deleted node
+ nb2(n2).erase( nb2(n2).begin() + iter );
+ } else if( m1.node > n1 ) {
+ // update this entry and the corresponding dual of the neighboring node of type 1
+ m1.iter = iter;
+ m1.node--;
+ nb1( m1.node, m1.dual ).dual = iter;
+ iter++;
+ } else {
+ // skip
+ iter++;
+ }
+ }
+ }
+}
+
+
+/// Remove node of type 2 and all incident edges.
+void BipartiteGraph::erase2( size_t n2 ) {
+ assert( n2 < nr2() );
+ // Erase neighbor entry of node n2
+ _nb2.erase( _nb2.begin() + n2 );
+ // Adjust neighbor entries of nodes of type 1
+ for( size_t n1 = 0; n1 < nr1(); n1++ ) {
+ for( size_t iter = 0; iter < nb1(n1).size(); ) {
+ Neighbor &m2 = nb1(n1, iter);
+ if( m2.node == n2 ) {
+ // delete this entry, because it points to the deleted node
+ nb1(n1).erase( nb1(n1).begin() + iter );
+ } else if( m2.node > n2 ) {
+ // update this entry and the corresponding dual of the neighboring node of type 2
+ m2.iter = iter;
+ m2.node--;
+ nb2( m2.node, m2.dual ).dual = iter;
+ iter++;
+ } else {
+ // skip
+ iter++;
+ }
+ }
+ }
+}
+
+
+/// Calculate second-order neighbors (i.e., neighbors of neighbors) of node n1 of type 1.
+/** If include == true, include n1 itself, otherwise exclude n1.
+ */
+std::vector<size_t> BipartiteGraph::delta1( size_t n1, bool include ) const {
+ std::vector<size_t> result;
+ foreach( const Neighbor &n2, nb1(n1) )
+ foreach( const Neighbor &m1, nb2(n2) )
+ if( include || (m1 != n1) )
+ result.push_back( m1 );
+ // remove duplicates
+ std::vector<size_t>::iterator it = std::unique( result.begin(), result.end() );
+ result.erase( it, result.end() );
+ return result;
+}
+
+
+/// Calculate second-order neighbors (i.e., neighbors of neighbors) of node n2 of type 2.
+/** If include == true, include n2 itself, otherwise exclude n2.
+ */
+std::vector<size_t> BipartiteGraph::delta2( size_t n2, bool include ) const {
+ std::vector<size_t> result;
+ foreach( const Neighbor &n1, nb2(n2) )
+ foreach( const Neighbor &m2, nb1(n1) )
+ if( include || (m2 != n2) )
+ result.push_back( m2 );
+ // remove duplicates
+ std::vector<size_t>::iterator it = std::unique( result.begin(), result.end() );
+ result.erase( it, result.end() );
+ return result;
+}
+
+
+/// Returns true if the graph is connected
+bool BipartiteGraph::isConnected() const {
+ if( nr1() == 0 ) {
+ return true;
+ } else {
+ std::vector<bool> incomponent1( nr1(), false );
+ std::vector<bool> incomponent2( nr2(), false );
+
+ incomponent1[0] = true;
+ bool found_new_nodes;
+ do {
+ found_new_nodes = false;
+
+ // For all nodes of type 2, check if they are connected with the (growing) component
+ for( size_t n2 = 0; n2 < nr2(); n2++ )
+ if( !incomponent2[n2] ) {
+ foreach( const Neighbor &n1, nb2(n2) ) {
+ if( incomponent1[n1] ) {
+ found_new_nodes = true;
+ incomponent2[n2] = true;
+ break;
+ }
+ }
+ }
+
+ // For all nodes of type 1, check if they are connected with the (growing) component
+ for( size_t n1 = 0; n1 < nr1(); n1++ )
+ if( !incomponent1[n1] ) {
+ foreach( const Neighbor &n2, nb1(n1) ) {
+ if( incomponent2[n2] ) {
+ found_new_nodes = true;
+ incomponent1[n1] = true;
+ break;
+ }
+ }
+ }
+ } while( found_new_nodes );
+
+ // Check if there are remaining nodes (not in the component)
+ bool all_connected = true;
+ for( size_t n1 = 0; (n1 < nr1()) && all_connected; n1++ )
+ if( !incomponent1[n1] )
+ all_connected = false;
+ for( size_t n2 = 0; (n2 < nr2()) && all_connected; n2++ )
+ if( !incomponent2[n2] )
+ all_connected = false;
+
+ return all_connected;
+ }
+}
+
+
+/// Returns true if the graph is a tree, i.e., if it is singly connected and connected.
+/** This is equivalent to whether for each pair of vertices in the graph, there exists
+ * a unique path in the graph that starts at the first and ends at the second vertex.
+ */
+bool BipartiteGraph::isTree() const {
+ using namespace std;
+ vector<levelType> levels;
+
+ bool foundCycle = false;
+ size_t nr_1 = 0;
+ size_t nr_2 = 0;
+
+ if( nr1() == 0 || nr2() == 0 )
+ return true;
+ else {
+ levelType newLevel;
+ do {
+ newLevel.ind1.clear();
+ newLevel.ind2.clear();
+ if( levels.size() == 0 ) {
+ size_t n1 = 0;
+ // add n1 to ind1
+ newLevel.ind1 = vector<size_t>( 1, n1 );
+ // add all neighbors of n1 to ind2
+ newLevel.ind2.reserve( nb1(n1).size() );
+ foreach( const Neighbor &n2, nb1(n1) )
+ newLevel.ind2.push_back( n2 );
+ } else {
+ const levelType &prevLevel = levels.back();
+ // build newLevel.ind1
+ foreach( size_t n2, prevLevel.ind2 ) { // for all n2 in the previous level
+ foreach( const Neighbor &n1, nb2(n2) ) { // for all neighbors n1 of n2
+ if( find( prevLevel.ind1.begin(), prevLevel.ind1.end(), n1 ) == prevLevel.ind1.end() ) { // n1 not in previous level
+ if( find( newLevel.ind1.begin(), newLevel.ind1.end(), n1 ) != newLevel.ind1.end() )
+ foundCycle = true; // n1 already in new level: we found a cycle
+ else
+ newLevel.ind1.push_back( n1 ); // add n1 to new level
+ }
+ if( foundCycle )
+ break;
+ }
+ if( foundCycle )
+ break;
+ }
+ // build newLevel.ind2
+ foreach( size_t n1, newLevel.ind1 ) { // for all n1 in this level
+ foreach( const Neighbor &n2, nb1(n1) ) { // for all neighbors n2 of n1
+ if( find( prevLevel.ind2.begin(), prevLevel.ind2.end(), n2 ) == prevLevel.ind2.end() ) { // n2 not in previous level
+ if( find( newLevel.ind2.begin(), newLevel.ind2.end(), n2 ) != newLevel.ind2.end() )
+ foundCycle = true; // n2 already in new level: we found a cycle
+ else
+ newLevel.ind2.push_back( n2 ); // add n2 to new level
+ }
+ if( foundCycle )
+ break;
+ }
+ if( foundCycle )
+ break;
+ }
+ }
+ levels.push_back( newLevel );
+ nr_1 += newLevel.ind1.size();
+ nr_2 += newLevel.ind2.size();
+ } while( ((newLevel.ind1.size() != 0) || (newLevel.ind2.size() != 0)) && !foundCycle );
+ if( nr_1 == nr1() && nr_2 == nr2() && !foundCycle )
+ return true;
+ else
+ return false;
+ }
+}
+
+
+/// Stream to output stream os in graphviz .dot syntax
+void BipartiteGraph::display( std::ostream& os ) const {
+ using namespace std;
+ os << "graph G {" << endl;
+ os << "node[shape=circle,width=0.4,fixedsize=true];" << endl;
+ for( size_t n1 = 0; n1 < nr1(); n1++ )
+ os << "\tx" << n1 << ";" << endl;
+ os << "node[shape=box,width=0.3,height=0.3,fixedsize=true];" << endl;
+ for( size_t n2 = 0; n2 < nr2(); n2++ )
+ os << "\ty" << n2 << ";" << endl;
+ for( size_t n1 = 0; n1 < nr1(); n1++ )
+ foreach( const Neighbor &n2, nb1(n1) )
+ os << "\tx" << n1 << " -- y" << n2 << ";" << endl;
+ os << "}" << endl;
+}
+
+
+/// Checks internal consistency
+void BipartiteGraph::check() const {
+ size_t N1 = nr1();
+ size_t N2 = nr2();
+ for( size_t n1 = 0; n1 < N1; n1++ ) {
+ size_t iter = 0;
+ foreach( const Neighbor &n2, nb1(n1) ) {
+ assert( n2.iter == iter );
+ assert( n2.node < N2 );
+ assert( n2.dual < nb2(n2).size() );
+ assert( nb2(n2, n2.dual) == n1 );
+ iter++;
+ }
+ }
+ for( size_t n2 = 0; n2 < N2; n2++ ) {
+ size_t iter = 0;
+ foreach( const Neighbor &n1, nb2(n2) ) {
+ assert( n1.iter == iter );
+ assert( n1.node < N1 );
+ assert( n1.dual < nb1(n1).size() );
+ assert( nb1(n1, n1.dual) == n2 );
+ iter++;
+ }
+ }
+}
+
+
+} // end of namespace dai
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