code: ///////////////////////////////////////////////////////////////////////////
  //                   __                _      _   ________               //
  //                  / /   ____  ____ _(_)____/ | / / ____/               //
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  //               /_____/\____/\__, /_/\___/_/ |_/\____/                  //
  //                           /____/                                      //
  //                                                                       //
  //               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.knowledgecompilation.bdds.orderings;
  
  import static org.logicng.knowledgecompilation.bdds.orderings.MinToMaxOrdering.sortProfileByOccurrence;
  
  import org.logicng.formulas.Formula;
  import org.logicng.formulas.Variable;
  import org.logicng.functions.VariableProfileFunction;
  
  import java.util.ArrayList;
  import java.util.Comparator;
  import java.util.List;
  import java.util.Map;
  
  /**
   * A BDD variable ordering sorting the variables from maximal to minimal occurrence
   * in the input formula.  If two variables have the same number of occurrences, their
   * ordering according to their DFS ordering will be considered.
   * @version 2.0.0
   * @since 1.4.0
   */
  public final class MaxToMinOrdering implements VariableOrderingProvider {
  
      private final VariableProfileFunction profileFunction = VariableProfileFunction.get();
      private final DFSOrdering dfsOrdering = new DFSOrdering();
  
      @Override
      public List<Variable> getOrder(final Formula formula) {
          final Map<Variable, Integer> profile = formula.apply(this.profileFunction);
          final List<Variable> dfs = this.dfsOrdering.getOrder(formula);
  
          final Comparator<Map.Entry<Variable, Integer>> comparator = (o1, o2) -> {
              final int occComp = o1.getValue().compareTo(o2.getValue());
              if (occComp != 0) {
                  return occComp;
              }
              final int index1 = dfs.indexOf(o1.getKey());
              final int index2 = dfs.indexOf(o2.getKey());
              return index1 - index2;
          };
          final Map<Variable, Integer> sortedProfile = sortProfileByOccurrence(profile, comparator);
          final List<Variable> order = new ArrayList<>(sortedProfile.size());
          for (final Map.Entry<Variable, Integer> entry : sortedProfile.entrySet()) {
              order.add(entry.getKey());
          }
          return order;
      }
  }
  