java - 将整数数组推送到 ArrayList

Question

我被困在将整数数组序列推送到 arraylist 的非常基本的方法中。我正在尝试针对问题 K Combinations of set of Integers 更改多基因润滑剂的解决方案这样我就不会打印它们，而是将它们推送到一个数组列表中。

我的代码:

public class Test {

    static ArrayList<String> combinations;
    public static void main(String args[]) {
        Integer[] a3 = { 1, 2, 3, 4, 5 };
        comb(a3, 2);
    }
    public static void comb(Integer[] items, int k) {
        Arrays.sort(items);
        combinations = new ArrayList<String>();
        ArrayList<String> c1 = new ArrayList<String>();
        c1 = kcomb(items, 0, k, new Integer[k]);
        System.out.println("from comb");
        for (String x : c1) {
            System.out.println(x);
        }
    }
    public static ArrayList<String> kcomb(Integer[] items, int n, int k,
            Integer[] arr) {
        if (k == 0) {
            combinations.add(Arrays.toString(arr));
        } else {
            for (int i = n; i <= items.length - k; i++) {
                arr[arr.length - k] = items[i];
                kcomb(items, i + 1, k - 1, arr);
            }
        }
        return combinations;
    }
}

输出:

from comb
[1, 2]
[1, 3]
[1, 4]
[1, 5]
[2, 3]
[2, 4]
[2, 5]
[3, 4]
[3, 5]
[4, 5]

但是当我如下将 ArrayList 的类型从 String 更改为 Integer[] 时，我得到了冗余输出。

更改代码

public class Test {

    static ArrayList<Integer[]> combinations;
    public static void main(String args[]) {
        Integer[] a3 = { 1, 2, 3, 4, 5 };
        comb(a3, 2);
    }
    public static void comb(Integer[] items, int k) {
        Arrays.sort(items);
        combinations = new ArrayList<Integer[]>();
        ArrayList<Integer[]> c1 = new ArrayList<Integer[]>();
        c1 = kcomb(items, 0, k, new Integer[k]);
        System.out.println("from comb");
        for (Integer[] x : c1) {
            System.out.println(Arrays.toString(x));
        }
    }
    public static ArrayList<Integer[]> kcomb(Integer[] items, int n, int k,
            Integer[] arr) {
        if (k == 0) {
            combinations.add(arr);
        } else {
            for (int i = n; i <= items.length - k; i++) {
                arr[arr.length - k] = items[i];
                kcomb(items, i + 1, k - 1, arr);
            }
        }
        return combinations;
    }
}

输出:

from comb
[4, 5]
[4, 5]
[4, 5]
[4, 5]
[4, 5]
[4, 5]
[4, 5]
[4, 5]
[4, 5]
[4, 5]

谁能帮我指出我做错了什么......

谢谢，萨拉斯

Answer 1

public class Test {

    static ArrayList<Integer[]> combinations;
    public static void main(String args[]) {
        Integer[] a3 = { 1, 2, 3, 4, 5 };
        comb(a3, 2);
    }
    public static void comb(Integer[] items, int k) {
        Arrays.sort(items);
        combinations = new ArrayList<Integer[]>();
        ArrayList<Integer[]> c1 = new ArrayList<Integer[]>();
        c1 = kcomb(items, 0, k, new Integer[k]);
        System.out.println("from comb");
        for (Integer[] x : c1) {
            System.out.println(Arrays.toString(x));
        }
    }
    public static ArrayList<Integer[]> kcomb(Integer[] items, int n, int k,
            Integer[] arr) {
        if (k == 0) {
            combinations.add(arr);
        } else {
            for (int i = n; i <= items.length - k; i++) {
                Integer[] arr1 = new Integer[arr.length];
                System.arraycopy(arr, 0, arr1, 0, arr.length);
                arr1[arr.length - k] = items[i];
                kcomb(items, i + 1, k - 1, arr1);
            }
        }
        return combinations;
    }
}