[Java] asked 幂集

package tree;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class Mi {
    public static List<Integer> a = new ArrayList<>();
    public static List<Integer> mi = new LinkedList<>();
    public static void getMi(int i) {
        if (i > a.size() - 1) show(mi);
        else {
            mi.add(a.get(i));
            getMi(i + 1);
            mi.remove(mi.size() - 1);
            getMi(i + 1);
        }
    }
    public static void show(List<Integer> list) {
        System.out.print("{");
        for (int n : list) {
            System.out.print(n + ",");
        }
        System.out.print("}");
    }
    public static void main(String[] args) {
        for (int i = 0;i < 3; i ++) {
            a.add(i);
        }
        getMi(0);
    }
}

class Note1 {
    int data;
    Note1 next;
}