转自 博客地址

算法把列表分为两个列表，然后递归地把左边列表的项移到右边列表
初次使用Markdown，排版十分猥琐，请求原谅= .=

    import java.util.*;
    public class Test{

    private static int NUM = 3;
    static List<List<String>> finalResult=new ArrayList();

    static void print(List l){
        for(Object s:l){
            System.out.print(s);
        }
    }
    
    private static void sort(List datas, List target) {
        if (target.size() == NUM) {
            finalResult.add(target);
            System.out.println();
            return;
        }
        for (int i = 0; i < datas.size(); i++) {
            List newDatas = new ArrayList(datas);   //注意这里是创建了两个新的List，原来的List将不会被操作修改
            List newTarget = new ArrayList(target);
            newTarget.add(newDatas.get(i));
            newDatas.remove(i);
            print(datas);   //这两个print的作用是辅助理解递归过程
            System.out.print("  ");
            print(target);
            System.out.println();
            sort(newDatas, newTarget);
        }
    }

    public static void main(String[] args) {
        String[] datas = new String[] { "a", "b", "c", "d" };
        sort(Arrays.asList(datas), new ArrayList());
        System.out.println("the Final Result:");
        Iterator<List<String>> i=finalResult.iterator();
        while(i.hasNext()){
            System.out.println(i.next());
        }
    }
}

</code>
省略了过程输出，最终结果输出如下：

the Final Result:
[a, b, c] [a, b, d] [a, c, b] [a, c, d] [a, d, b]
[a, d, c] [b, a, c] [b, a, d] [b, c, a] [b, c, d]
[b, d, a] [b, d, c] [c, a, b] [c, a, d] [c, b, a]
[c, b, d] [c, d, a] [c, d, b] [d, a, b] [d, a, c]
[d, b, a] [d, b, c] [d, c, a] [d, c, b]