帮帮忙，排列出可能的组合解决方案

/*
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package javatest;

/**
 *
 * @author ZangXT
 */
public class Main {

    public static void main(String[] args) {
        int a[] = {1, 2, 3,4};
        perm(a, 0, a.length - 1);
    }

    public static void perm(int[] buf, int start, int end) {
        if (start == end) {
            for (int i = 0; i <= end; i++) {
                System.out.print(buf[i] + " ");
            }
            System.out.println();
        } else {
            for (int i = start; i <= end; i++) {
                swap(buf, start, i);
                perm(buf, start + 1, end);
                swap(buf, start, i);
            }
        }
    }

    private static void swap(int buf[], int i, int j) {
        int temp = buf[i];
        buf[i] = buf[j];
        buf[j] = temp;
    }
}

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好麻烦，数值少还好，一旦数值很大时就会占用很大

------解决方案--------------------