/******************************************************************************* * Copyright (c) 2014 Opt4J * * 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: * * The above copyright notice and this permission notice shall be included in all * copies or substantial portions of the Software. * * 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.opt4j.operators.neighbor; import java.util.Collections; import java.util.Random; import org.opt4j.core.common.random.Rand; import org.opt4j.core.genotype.PermutationGenotype; import com.google.inject.Inject; /** * <p> * Neighbor for the {@link PermutationGenotype}. Reverts a sublist. * </p> * * <p> * Given a permutation {@code 1 2 3 4 5 6 7 8}, this might result in * {@code 1 2 7 6 5 4 3 8}. * </p> * * @author lukasiewycz * */ public class NeighborPermutationRevert implements NeighborPermutation { protected final Random random; /** * Constructs a {@link NeighborPermutationRevert} operator for the * {@link PermutationGenotype}. * * @param random * the random number generator */ @Inject public NeighborPermutationRevert(Rand random) { this.random = random; } /* * (non-Javadoc) * * @see * org.opt4j.operator.neighbor.Neighbor#neighbor(org.opt4j.core.Genotype) */ @Override public void neighbor(PermutationGenotype<?> genotype) { int size = genotype.size(); if (size > 1) { int a = random.nextInt(size - 1); int b; do { b = a + random.nextInt(size - a); } while (b == a); while (a < b) { Collections.swap(genotype, a, b); a++; b--; } } } }