code: ///////////////////////////////////////////////////////////////////////////
  //                   __                _      _   ________               //
  //                  / /   ____  ____ _(_)____/ | / / ____/               //
  //                 / /   / __ \/ __ `/ / ___/  |/ / / __                 //
  //                / /___/ /_/ / /_/ / / /__/ /|  / /_/ /                 //
  //               /_____/\____/\__, /_/\___/_/ |_/\____/                  //
  //                           /____/                                      //
  //                                                                       //
  //               The Next Generation Logic Library                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  //                                                                       //
  //  Copyright 2015-20xx Christoph Zengler                                //
  //                                                                       //
  //  Licensed under the Apache License, Version 2.0 (the "License");      //
  //  you may not use this file except in compliance with the License.     //
  //  You may obtain a copy of the License at                              //
  //                                                                       //
  //  http://www.apache.org/licenses/LICENSE-2.0                           //
  //                                                                       //
  //  Unless required by applicable law or agreed to in writing, software  //
  //  distributed under the License is distributed on an "AS IS" BASIS,    //
  //  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or      //
  //  implied.  See the License for the specific language governing        //
  //  permissions and limitations under the License.                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  
  package org.logicng.graphs.datastructures;
  
  import java.util.LinkedHashSet;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  
  /**
   * A node in a hypergraph.
   * @param <T> the content type of the graph's nodes
   * @version 2.0.0
   * @since 1.4.0
   */
  public final class HypergraphNode<T> {
  
      private final Hypergraph<T> graph;
      private final T content;
      private final LinkedHashSet<HypergraphEdge<T>> edges;
  
      /**
       * Constructs a new hypergraph node for a given graph and content.
       * @param graph   the graph for this node
       * @param content the content of this node
       */
      public HypergraphNode(final Hypergraph<T> graph, final T content) {
          this.graph = graph;
          this.content = content;
          this.edges = new LinkedHashSet<>();
          this.graph.addNode(this);
      }
  
      /**
       * Returns the hypergraph of this node.
       * @return the hypergraph of this node
       */
      public Hypergraph<T> graph() {
          return this.graph;
      }
  
      /**
       * Returns the content of this node.
       * @return the content of this node
       */
      public T content() {
          return this.content;
      }
  
      /**
       * Returns the edges which are connected with this node.
       * @return the edges which are connected with this node
       */
      public Set<HypergraphEdge<T>> edges() {
          return this.edges;
      }
  
      /**
       * Adds an edge to this node.
       * @param edge the edge
       */
      public void addEdge(final HypergraphEdge<T> edge) {
          this.edges.add(edge);
      }
  
      /**
       * Computes the tentative new location for this node (see Aloul, Markov, and Sakallah).
       * @param nodeOrdering the node ordering for which the COG is computed
       * @return the tentative new location for this node
       */
      public double computeTentativeNewLocation(final Map<HypergraphNode<T>, Integer> nodeOrdering) {
          double newLocation = 0;
          for (final HypergraphEdge<T> edge : this.edges) {
              newLocation += edge.centerOfGravity(nodeOrdering);
          }
          return newLocation / this.edges.size();
      }
  
      @Override
      public boolean equals(final Object o) {
          if (this == o) {
              return true;
          }
          if (o == null || getClass() != o.getClass()) {
              return false;
          }
          final HypergraphNode<?> that = (HypergraphNode<?>) o;
          return Objects.equals(this.graph, that.graph) &&
                  Objects.equals(this.content, that.content);
      }
  
      @Override
      public int hashCode() {
          return Objects.hash(this.graph, this.content);
      }
  
      @Override
      public String toString() {
          return "HypergraphNode{" +
                  "content=" + this.content +
                  '}';
      }
  }
  