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协助编写一个递归函数，该函数汇总了Java中的数组列表

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我正在尝试编写一个递归程序，它将数组列表的总和相加 . 它需要使用辅助函数，如下所示 .

我没有看到我做错了什么，但我认为这与未能让程序在添加后从列表中删除项目有关 . 谁能帮助我？

编辑：让我用伪代码解释我的逻辑：我想让程序识别数组列表中的项目并将其存储为double sum . 然后通过递归传递，我想通过移动数组列表中的项目并将它们添加到double sum来继续重复此过程 .

public static double sum (double[] a) {
    double sum = 0;
    return sumHelper (a, a.length-1, sum); // TODO
}

public static double sumHelper (double[] a, int i, double sum) 
{
    if (a.length == 0) {
        return sumHelper (a, a-1, sum);
    }
    else {
        sum = sum + a[i];
        i = i-1;
        a.length -1; // THIS LINE DOESN'T WORK
        return sumHelper (a, a-1, sum);
    }   
    return sum;
}

public static void main (String[] args) {
    double[] list0 = new double[] {};
    double[] list1 = new double[] { 5 };
    double[] list2 = new double[] { -3, 5 };
    double[] list3 = new double[] { 2, -3, 5 };
    double[] list4 = new double[] { -1, 2, -3, 5 };
    double[] list5 = new double[] { 33, 44, 55 };

    System.out.println("Display the sum of the array contents");
    System.out.println ("list5: " +sum (list5));
    System.out.println ("list0: " +sum (list0));
    System.out.println ("list1: " +sum (list1));
    System.out.println ("list2: " +sum (list2));
    System.out.println ("list3: " +sum (list3));
    System.out.println ("list4: " +sum (list4));
java recursion

2 回答

  • 0

    这是你想要做的吗？

    public static double sum (double[] a) {
    double sum = 0;
    return sumHelper (a, a.length-1, sum); // TODO
}

public static double sumHelper (double[] a, int i, double sum) 
{
    if (i < 0) { 
        return sum;
    }
    else {
        sum = sum + a[i];
        i = i-1;
        return sumHelper (a, i, sum);
    }   
}

public static void main(String[] args) {
    double[] list0 = new double[] {};
    double[] list1 = new double[] { 5 };
    double[] list2 = new double[] { -3, 5 };
    double[] list3 = new double[] { 2, -3, 5 };
    double[] list4 = new double[] { -1, 2, -3, 5 };
    double[] list5 = new double[] { 33, 44, 55 };

    System.out.println("Display the sum of the array contents");
    System.out.println ("list5: " +sum (list5));
    System.out.println ("list0: " +sum (list0));
    System.out.println ("list1: " +sum (list1));
    System.out.println ("list2: " +sum (list2));
    System.out.println ("list3: " +sum (list3));
    System.out.println ("list4: " +sum (list4));

}

    结果：

    显示数组内容列表的总和5：132.0 list0：0.0 list1：5.0 list2：2.0 list3：4.0 list4：3.0

    回复于
  • 1

    你错放了变量，a-1而不是i . 并且数组将从0索引开始，因此您需要将元素添加到0索引 .

    static double[] list0 = new double[] {};
        static double[] list1 = new double[] { 5 };
        static double[] list2 = new double[] { -3, 5 };
        static double[] list3 = new double[] { 2, -3, 5 };
        static double[] list4 = new double[] { -1, 2, -3, 5 };
        static double[] list5 = new double[] { 33, 44, 55 };
        public static void main(String[] args) {
            // TOsuDO Auto-generated method stub
            System.out.println("Display the sum of the array contents");
            System.out.println ("list5: " +sum (list5));
            System.out.println ("list0: " +sum (list0));
            System.out.println ("list1: " +sum (list1));
            System.out.println ("list2: " +sum (list2));
            System.out.println ("list3: " +sum (list3));
            System.out.println ("list4: " +sum (list4));
        }
        public static double sum (double[] a) {
            double sum = 0;
            return sumHelper (a, a.length-1, sum); // TODO
        }
        public static double sumHelper (double[] a, int i, double sum) 
        {
            if (i == -1) {
                {
                    System.out.println("Added all the elements");
                    return sum;
                }
            }
            else {
                sum = sum + a[i];
                i = i-1;
                //a.length -1; // THIS LINE DOESN'T WORK
                return sumHelper (a, i, sum);
            }
        }
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