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OptaPlanner solves planning problems. This lightweight, embeddable planning engine implements powerful and scalable algorithms to optimize business resource scheduling and planning. This module contains the examples which demonstrate how to use it in a normal Java application.

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/*
 * Copyright 2012 Red Hat, Inc. and/or its affiliates.
 *
 * 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.optaplanner.examples.nqueens.solver.score;

import java.util.ArrayList;
import java.util.List;

import org.optaplanner.core.api.score.buildin.simple.SimpleScore;
import org.optaplanner.core.impl.score.director.incremental.AbstractIncrementalScoreCalculator;
import org.optaplanner.examples.nqueens.domain.NQueens;
import org.optaplanner.examples.nqueens.domain.Queen;
import org.optaplanner.examples.nqueens.domain.Row;

public class NQueensBasicIncrementalScoreCalculator extends AbstractIncrementalScoreCalculator {

    private List insertedQueenList;
    private int score;

    @Override
    public void resetWorkingSolution(NQueens nQueens) {
        insertedQueenList = new ArrayList<>(nQueens.getN());
        score = 0;
        for (Queen queen : nQueens.getQueenList()) {
            insert(queen);
        }
    }

    @Override
    public void beforeEntityAdded(Object entity) {
        // Do nothing
    }

    @Override
    public void afterEntityAdded(Object entity) {
        insert((Queen) entity);
    }

    @Override
    public void beforeVariableChanged(Object entity, String variableName) {
        retract((Queen) entity);
    }

    @Override
    public void afterVariableChanged(Object entity, String variableName) {
        insert((Queen) entity);
    }

    @Override
    public void beforeEntityRemoved(Object entity) {
        retract((Queen) entity);
    }

    @Override
    public void afterEntityRemoved(Object entity) {
        // Do nothing
    }

    private void insert(Queen queen) {
        Row row = queen.getRow();
        if (row != null) {
            for (Queen otherQueen : insertedQueenList) {
                if (queen.getRowIndex() == otherQueen.getRowIndex()) {
                    score--;
                }
                if (queen.getAscendingDiagonalIndex() == otherQueen.getAscendingDiagonalIndex()) {
                    score--;
                }
                if (queen.getDescendingDiagonalIndex() == otherQueen.getDescendingDiagonalIndex()) {
                    score--;
                }
            }
            insertedQueenList.add(queen);
        }
    }

    private void retract(Queen queen) {
        Row row = queen.getRow();
        if (row != null) {
            insertedQueenList.remove(queen);
            for (Queen otherQueen : insertedQueenList) {
                if (queen.getRowIndex() == otherQueen.getRowIndex()) {
                    score++;
                }
                if (queen.getAscendingDiagonalIndex() == otherQueen.getAscendingDiagonalIndex()) {
                    score++;
                }
                if (queen.getDescendingDiagonalIndex() == otherQueen.getDescendingDiagonalIndex()) {
                    score++;
                }
            }
        }
    }

    @Override
    public SimpleScore calculateScore() {
        return SimpleScore.of(score);
    }

}