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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.app;

import java.util.List;

import org.optaplanner.core.api.solver.Solver;
import org.optaplanner.core.api.solver.SolverFactory;
import org.optaplanner.examples.nqueens.domain.NQueens;
import org.optaplanner.examples.nqueens.domain.Queen;
import org.optaplanner.examples.nqueens.persistence.NQueensGenerator;

public class NQueensHelloWorld {

    public static void main(String[] args) {
        // Build the Solver
        SolverFactory solverFactory = SolverFactory.createFromXmlResource(
                "org/optaplanner/examples/nqueens/solver/nqueensSolverConfig.xml");
        Solver solver = solverFactory.buildSolver();

        // Load a problem with 8 queens
        NQueens unsolved8Queens = new NQueensGenerator(true).createNQueens(8);

        // Solve the problem
        NQueens solved8Queens = solver.solve(unsolved8Queens);

        // Display the result
        System.out.println("\nSolved 8 queens:\n" + toDisplayString(solved8Queens));
    }

    public static String toDisplayString(NQueens nQueens) {
        StringBuilder displayString = new StringBuilder();
        int n = nQueens.getN();
        List queenList = nQueens.getQueenList();
        for (int row = 0; row < n; row++) {
            for (int column = 0; column < n; column++) {
                Queen queen = queenList.get(column);
                if (queen.getColumn().getIndex() != column) {
                    throw new IllegalStateException("The queenList is not in the expected order.");
                }
                displayString.append(" ");
                if (queen.getRow() != null && queen.getRow().getIndex() == row) {
                    displayString.append("Q");
                } else {
                    displayString.append("_");
                }
            }
            displayString.append("\n");
        }
        return displayString.toString();
    }

}