org.drools.planner.examples.nqueens.domain.solution.RowStrengthWeightFactory Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of drools-planner-examples Show documentation

Drools Planner optimizes automated planning by combining metaheuristic search algorithms with rule engine powered score calculation. This is the drools-planner-examples module which contains examples on how to use Drools Planner.

There is a newer version: 6.0.0.Alpha9

Show newest version

/*
 * Copyright 2011 JBoss Inc
 *
 * 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.drools.planner.examples.nqueens.domain.solution;

import org.apache.commons.lang.builder.CompareToBuilder;
import org.drools.planner.api.domain.variable.PlanningValueStrengthWeightFactory;
import org.drools.planner.core.solution.Solution;
import org.drools.planner.examples.nqueens.domain.NQueens;
import org.drools.planner.examples.nqueens.domain.Queen;
import org.drools.planner.examples.nqueens.domain.Row;

public class RowStrengthWeightFactory implements PlanningValueStrengthWeightFactory {

    public Comparable createStrengthWeight(Solution solution, Object planningValue) {
        NQueens nQueens = (NQueens) solution;
        Row row = (Row) planningValue;
        int distanceFromMiddle = calculateDistanceFromMiddle(nQueens.getN(), row.getIndex());
        return new RowStrengthWeight(row, distanceFromMiddle);
    }

    private static int calculateDistanceFromMiddle(int n, int columnIndex) {
        int middle = n / 2;
        int distanceFromMiddle = Math.abs(columnIndex - middle);
        if ((n % 2 == 0) && (columnIndex < middle)) {
            distanceFromMiddle--;
        }
        return distanceFromMiddle;
    }

    public static class RowStrengthWeight implements Comparable {

        private final Row row;
        private final int distanceFromMiddle;

        public RowStrengthWeight(Row row, int distanceFromMiddle) {
            this.row = row;
            this.distanceFromMiddle = distanceFromMiddle;
        }

        public int compareTo(RowStrengthWeight other) {
            return new CompareToBuilder()
                    // The stronger rows have a lower distance to the middle
                    .append(other.distanceFromMiddle, distanceFromMiddle) // Decreasing (but this is debatable)
                    .append(row.getIndex(), other.row.getIndex())
                    .toComparison();
        }

    }

}