Random 随机变异爬山问题

嗨，我想写一些简单的代码，用随机变异爬山来解决旅行推销员的问题。我已经创建了一个旅游类：-

import java.util.ArrayList;
import java.util.Collections;

public class Tour 
{
    private ArrayList<Integer> tour;

    // Specified tour
    public Tour(ArrayList<Integer> tour) { this.tour = tour; }

    // Random tour
    public Tour(int size) 
    {
        // Initalize tour with size
        tour = new ArrayList<Integer>(size);
        // Add integers up to size into ArrayList
        for (int i=0; i<size; ++i) {tour.add(i);}
        // Shuffle ArrayList
        Collections.shuffle(tour);
    }

    ArrayList<Integer> getTour() {return tour;}

    void printTour()
    {
        for (int i=0; i<tour.size(); ++i)
        {
            System.out.print(tour.get(i) + ", ");
        }
    }

    // Get the distance between all tour stops using a set of distances
    double getFitness (double[][] distances)
    {
        double s = 0;
        for (int i=0; i<tour.size()-1; ++i)
        {
            int a = tour.get(i);
            int b = tour.get(i+1);
            s += distances[a][b];
        }
        int start_city = tour.get(0);
        int end_city = tour.get(tour.size()-1);
        s += distances[end_city][start_city];
        return s;
    }

    // Makes a small change to the tour
    void smallChange()
    {
        // Change random index values to swap
        int indexfirst = CS2004.UI(0, tour.size()-1);
        int indexsecond = CS2004.UI(0, tour.size()-1);

        // Checks to make sure index values are not the same
        while (indexsecond == indexfirst)
        {
            indexsecond = CS2004.UI(0, tour.size()-1);
        }

        // Store city value in temp variable
        int indexTemp = tour.get(indexfirst);

        // Swap values
        tour.set(indexfirst, tour.get(indexsecond));
        tour.set(indexsecond, indexTemp);
    }

}

---

定义了吗？是的，最后我不得不将“oldSol=newtour（sol.getTour（））；”更改为“oldSol=newtour（（ArrayList）sol.getTour（）.clone（））；”，但我不太确定为什么这样做有效？

public static Tour RMHC(double[][] distances, int iter)
{
    Tour sol = new Tour(distances.length);
    double oldFitness;
    double fitness = 0;
    Tour oldSol=null;

    for (int i=0;i<iter;i++)
    {
        oldSol = null;
        // Make old solution equal to solution before change
        oldSol = new Tour(sol.getTour());

        System.out.println(oldSol.getTour());
        // Calculate old fitness for comparison
        oldFitness = sol.getFitness(distances); 

        // Change solution slightly
        sol.smallChange();

        // Calculate new fitness
        fitness = sol.getFitness(distances);

        /* Compare new fitness to old fitness 
         * set solution back to old solution and fitness to old fitness if 
         * new solution is not better */
        System.out.println(oldFitness + " " + fitness);
        if (fitness > oldFitness) {System.out.println(oldSol.getTour()); System.out.println(sol.getTour()); sol = null; sol = new Tour(oldSol.getTour()); fitness = oldFitness;}

        // Print iteration number and new fitness
        System.out.println("Iteration " + (i+1) + ", fitness: " + sol.getFitness(distances));
    }
    return(sol);
}

[11, 6, 13, 37, 23, 45, 34, 25, 16, 39, 5, 35, 31, 9, 27, 0, 10, 42, 30, 28, 4, 12, 33, 36, 2, 21, 17, 29, 18, 20, 32, 3, 15, 47, 26, 19, 46, 8, 22, 44, 7, 24, 43, 14, 41, 1, 38, 40]
155843.9387676824 159088.1701641078
[31, 6, 13, 37, 23, 45, 34, 25, 16, 39, 5, 35, 11, 9, 27, 0, 10, 42, 30, 28, 4, 12, 33, 36, 2, 21, 17, 29, 18, 20, 32, 3, 15, 47, 26, 19, 46, 8, 22, 44, 7, 24, 43, 14, 41, 1, 38, 40]
[31, 6, 13, 37, 23, 45, 34, 25, 16, 39, 5, 35, 11, 9, 27, 0, 10, 42, 30, 28, 4, 12, 33, 36, 2, 21, 17, 29, 18, 20, 32, 3, 15, 47, 26, 19, 46, 8, 22, 44, 7, 24, 43, 14, 41, 1, 38, 40]
Iteration 1, fitness: 159088.1701641078
[31, 6, 13, 37, 23, 45, 34, 25, 16, 39, 5, 35, 11, 9, 27, 0, 10, 42, 30, 28, 4, 12, 33, 36, 2, 21, 17, 29, 18, 20, 32, 3, 15, 47, 26, 19, 46, 8, 22, 44, 7, 24, 43, 14, 41, 1, 38, 40]
159088.1701641078 144709.1336957683
Iteration 2, fitness: 144709.1336957683
[31, 6, 13, 37, 7, 45, 34, 25, 16, 39, 5, 35, 11, 9, 27, 0, 10, 42, 30, 28, 4, 12, 33, 36, 2, 21, 17, 29, 18, 20, 32, 3, 15, 47, 26, 19, 46, 8, 22, 44, 23, 24, 43, 14, 41, 1, 38, 40]
144709.1336957683 143387.5110957744
Iteration 3, fitness: 143387.5110957744
[31, 6, 13, 37, 7, 45, 22, 25, 16, 39, 5, 35, 11, 9, 27, 0, 10, 42, 30, 28, 4, 12, 33, 36, 2, 21, 17, 29, 18, 20, 32, 3, 15, 47, 26, 19, 46, 8, 34, 44, 23, 24, 43, 14, 41, 1, 38, 40]
143387.5110957744 143565.3842060348
[31, 6, 13, 37, 7, 45, 22, 25, 16, 39, 5, 35, 14, 9, 27, 0, 10, 42, 30, 28, 4, 12, 33, 36, 2, 21, 17, 29, 18, 20, 32, 3, 15, 47, 26, 19, 46, 8, 34, 44, 23, 24, 43, 11, 41, 1, 38, 40]
[31, 6, 13, 37, 7, 45, 22, 25, 16, 39, 5, 35, 14, 9, 27, 0, 10, 42, 30, 28, 4, 12, 33, 36, 2, 21, 17, 29, 18, 20, 32, 3, 15, 47, 26, 19, 46, 8, 34, 44, 23, 24, 43, 11, 41, 1, 38, 40]