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.                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  
  /*
   * PBLib       -- Copyright (c) 2012-2013  Peter Steinke
   * <p>
   * Permission is hereby granted, free of charge, to any person obtaining a
   * copy of this software and associated documentation files (the
   * "Software"), to deal in the Software without restriction, including
   * without limitation the rights to use, copy, modify, merge, publish,
   * distribute, sublicense, and/or sell copies of the Software, and to
   * permit persons to whom the Software is furnished to do so, subject to
   * the following conditions:
   * <p>
   * The above copyright notice and this permission notice shall be included
   * in all copies or substantial portions of the Software.
   * <p>
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
   * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
   * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   */
  
  package org.logicng.cardinalityconstraints;
  
  import org.logicng.collections.LNGVector;
  import org.logicng.datastructures.EncodingResult;
  import org.logicng.formulas.Literal;
  import org.logicng.formulas.Variable;
  
  /**
   * Encodes that at most one variable is assigned value true.  Uses the commander encoding due to Klieber &amp; Kwon.
   * @version 2.0.0
   * @since 1.1
   */
  public final class CCAMOCommander implements CCAtMostOne {
  
      private final int k;
      private final LNGVector<Literal> literals;
      private final LNGVector<Literal> nextLiterals;
      private final LNGVector<Literal> currentLiterals;
      private EncodingResult result;
  
      /**
       * Constructs the commander AMO encoder with a given group size.
       * @param k the group size for the encoding
       */
      CCAMOCommander(final int k) {
          this.k = k;
          this.literals = new LNGVector<>();
          this.nextLiterals = new LNGVector<>();
          this.currentLiterals = new LNGVector<>();
      }
  
      @Override
      public void build(final EncodingResult result, final Variable... vars) {
          result.reset();
          this.result = result;
          this.currentLiterals.clear();
          this.nextLiterals.clear();
          for (final Variable var : vars) {
              this.currentLiterals.push(var);
          }
          this.encodeRecursive();
      }
  
      /**
       * Internal recursive encoding.
       */
      private void encodeRecursive() {
          boolean isExactlyOne = false;
          while (this.currentLiterals.size() > this.k) {
              this.literals.clear();
              this.nextLiterals.clear();
              for (int i = 0; i < this.currentLiterals.size(); i++) {
                  this.literals.push(this.currentLiterals.get(i));
                  if (i % this.k == this.k - 1 || i == this.currentLiterals.size() - 1) {
                      this.encodeNonRecursive(this.literals);
                      this.literals.push(this.result.newVariable());
                      this.nextLiterals.push(this.literals.back().negate());
                      if (isExactlyOne && this.literals.size() > 0) {
                          this.result.addClause(this.literals);
                      }
                      for (int j = 0; j < this.literals.size() - 1; j++) {
                          this.result.addClause(this.literals.back().negate(), this.literals.get(j).negate());
                      }
                      this.literals.clear();
                  }
              }
              this.currentLiterals.replaceInplace(this.nextLiterals);
              isExactlyOne = true;
          }
          this.encodeNonRecursive(this.currentLiterals);
          if (isExactlyOne && this.currentLiterals.size() > 0) {
              this.result.addClause(this.currentLiterals);
          }
      }
  
      /**
       * Internal non-recursive encoding.
       * @param literals the current literals
       */
      private void encodeNonRecursive(final LNGVector<Literal> literals) {
          if (literals.size() > 1) {
              for (int i = 0; i < literals.size(); i++) {
                  for (int j = i + 1; j < literals.size(); j++) {
                      this.result.addClause(literals.get(i).negate(), literals.get(j).negate());
                  }
              }
          }
      }
  
      @Override
      public String toString() {
          return this.getClass().getSimpleName();
      }
  }
  