约瑟夫环

package com.com.linklist;

public class yuesefu {
    public static void main(String[] args) {
        CircleSingleLinkedList link = new CircleSingleLinkedList();
        link.addBoy(5);
        link.showBoy();
        link.countboy(1,2,5);
    }
}

//创建一个环形的带向链表

class CircleSingleLinkedList {
    //创建一个first节点
    private Boy first = null;

    //添加小孩节点
    public void addBoy(int nums) {
        if (nums < 1) {
            System.out.println("nums值不正确");
            return;
        }
        Boy curBoy = null;//辅助指针
        for (int i = 1; i <= nums; i++) {
            Boy boy = new Boy(i);
            //入如果是第一个小孩
            if (i == 1) {
                first = boy;
                first.setNext(first);//构成环
                curBoy = first;//让cur指向第一个小孩

            } else {
                curBoy.setNext(boy);
                boy.setNext(first);
                curBoy = boy;
            }

        }

    }

    //遍历
    public void showBoy()
    {
        //判断是否为空
        if(first==null)
        {
            System.out.println("链表为空");
            return;
        }
        //因为first不能动 所以依然需要一个辅助指针
        Boy curBoy = first;

        while(true)
        {
            System.out.printf("小孩编号%d\n",curBoy.getNo());
            if(curBoy.getNext()==first)
            {
                break;
            }
            curBoy = curBoy.getNext();
        }

    }


    //从第几个小孩子开始，数几下，最初有多少小孩在圈中
    public void countboy(int startNo,int countNum,int nums) {
        if (first == null || startNo < 1 || startNo > nums) {
            System.out.println("参数有错误，请重新输入");
            return;
        }
        //辅助指针 最后存在尾部
        Boy helper = first;
        while (true) {
            if (helper.getNext() == first) {
                break;
            }
            helper = helper.getNext();
        }

        //报数之前从哪里开始 让first和help 移动k-1次 也就是从哪里开始
        for (int j = 0; j < startNo - 1; j++) {
            first = first.getNext();
            helper = helper.getNext();
        }

        //    Boy curBoy = first;
        //当小孩报数时 让first和helper指针同时移动m-1次  也就是数几次
//        for(int j=0;j<startNo-1;j++)
//        {
//          curBoy=first.getNext();
//          helper=helper.getNext();
//        }
//        first.setNext(curBoy);
        //当小孩报数时 让first和helper指针同时移动m-1次  也就是数几次
        //循环操作到只剩下最后一个
        while (true)
        {
            if(helper==first)
            {
                break;
            }
            for(int j=0;j<countNum-1;j++)
            {
                first=first.getNext();
                helper=helper.getNext();
            }
            System.out.printf("小孩%d出局\n",first.getNo());

            //临时销毁
            Boy pcur = first;

            first = first.getNext();
            helper.setNext(first);

            pcur=null;//java 可以自己垃圾回收机制销毁 可以不这样
        }

        System.out.printf("小孩%d胜利\n",first.getNo());
    }


}



class  Boy {

    private int no;
    private Boy next;

    public Boy(int no) {
        this.no = no;
    }

    public int getNo() {
        return no;
    }

    public void setNo(int no) {
        this.no = no;
    }

    public Boy getNext() {
        return next;
    }

    public void setNext(Boy next)
    {
        this.next=next;
    }

    @Override
    public String toString() {
        return "Boy{" +
                "no=" + no +
//                ", next=" + next +
                '}';
    }
}