Question

我一直试图通过我提供的代码对Double类型的二维数组进行排序，我的数组不包含任何0，但在排序后有几个0。

排序代码

Arrays.sort(merge, new Comparator<double[]>() {
            @Override
            public int compare(double[] o1, double[] o2) {
                return Double.compare(o1[4], o2[4]);
            }
        });

这是我的完整代码，我想根据数组[i] [4]进行排序即第四指数： -

public class EvoAlgo {

static int k = 40;//generations
static double al = 0, ah = 1, bl = -2, bh = 2, cl = -2, ch = 1, dl = 0.5, dh = 1;
static double m1 = 0.02, m2 = 0.22, m3 = -0.11, m4 = 0.22;

static double f(double a, double b, double c, double d) {

    return (2 * a * a) - (2.5 * a * b * c * c) + (4 * b * c * d) + (0.25 * c * d) - (0.2 * d * d);

}

static double[] mutate(double[] child) {
    double m = Math.random();
    if (m <= 0.25) {
        child[0] = child[0] * m1;
    } else if (m <= 0.5) {
        child[1] = child[1] * m2;

    } else if (m <= 0.75) {
        child[2] = child[2] * m3;

    } else {
        child[3] = child[3] * m4;
    }
    child[4] = f(child[0], child[1], child[2], child[3]);
    return child;
}

static double[][] initRandomPop() {

    double[][] initPop = new double[25][5];
    for (int i = 0; i < initPop.length; i++) {
        double ax = al + (Math.random() * ((ah - al) + 1));
        double bx = bl + (Math.random() * ((bh - bl) + 1));
        double cx = cl + (Math.random() * ((ch - cl) + 1));
        double dx = dl + (Math.random() * ((dh - dl) + 1));
        initPop[i][0] = ax;
        initPop[i][1] = bx;
        initPop[i][2] = cx;
        initPop[i][3] = dx;
        initPop[i][4] = f(ax, bx, cx, dx);
    }
    return initPop;
}

static double[][] merge(double[][] a, double[][] b) {
    double[][] merge = new double[a.length + b.length][5];
    for (int i = 0; i < a.length; i++) {
        merge[i] = a[i];
    }
    for (int i = a.length; i < b.length; i++) {
        merge[i] = a[i];
    }
    return merge;
}

static double[][] newPop(double[][] a) {
    double[][] newPop = new double[25][5];
    for (int i = 0; i < 25; i++) {
        newPop[i] = a[i];
    }
    return newPop;
}

public static void main(String[] args) {

    double[][] initPop = initRandomPop();
    double[][] child = new double[40][5];
    int cc = 0;
    for (int i = 0; i < k; i++) {
        for (int j = 0; j < 20; j++) {
            int ri1 = 0 + (int) (Math.random() * ((24 - 0) + 1));
            int ri2 = 0 + (int) (Math.random() * ((24 - 0) + 1));
            double[] ind1 = initPop[ri1];
            double[] ind2 = initPop[ri2];
            double[] c1 = new double[5];
            double[] c2 = new double[5];

            c1[0] = ind1[0];
            c1[1] = ind1[1];
            c1[2] = ind2[2];
            c1[3] = ind2[3];
            c1[4] = f(ind1[0], ind1[1], ind2[2], ind2[3]);
            c2[0] = ind2[0];
            c2[1] = ind2[1];
            c2[2] = ind1[2];
            c2[3] = ind1[3];
            c2[4] = f(ind2[0], ind2[1], ind1[2], ind1[3]);

            c1 = mutate(c1);
            c2 = mutate(c2);
            child[cc++] = c1;
            child[cc++] = c2;
        }
        double[][] merge = merge(child, initPop);

        Arrays.sort(merge, new Comparator<double[]>() {
            @Override
            public int compare(double[] o1, double[] o2) {
                return Double.compare(o1[4], o2[4]);
            }
        });
        for (int j = 0; j < merge.length; j++) {
            System.out.println(merge[j][4]);
        }
        initPop = newPop(merge);
        cc = 0;
    }
    System.out.println("Fittest Person On Earth " + initPop[0][4]);
}

}

Answer 1

0是默认值。它可以与null进行比较，因此很可能您会遇到数组字段未赋值的情况。

Answer 2

抱歉错误的问题！问题出在merge（）方法中。这是修复

static double[][] merge(double[][] a, double[][] b) {
    double[][] merge = new double[a.length + b.length][5];
    for (int i = 0; i < a.length; i++) {
        merge[i] = a[i];
    }
    int p = 0;
    for (int i = a.length; i < merge.length; i++) {
        merge[i] = b[p++];
    }
    return merge;
}

2D数组（双精度）排序自己给出0个值

2 个答案: