五、环形链表和约瑟夫问题

      一、引出问题

      约瑟夫问题：设编号为1，2，… n的n个人围坐一圈，约定编号为k（1<=k<=n）的人从1开始报数，数到m 的那个人出列，它的下一位又从1开始报数，数到m的那个人又出列，依次类推，直到所有人出列为止，由此产生一个出队编号的序列。
      例如编号为12345的环形链表，从1开始，则出队编号为：2—>4—>1—>5—>3.

      二、代码实现

package Jusepfu;

public class Josepfu {
    public static void main(String[] args) {
        CircleSingleLinkedList circleSingleLinkedList = new CircleSingleLinkedList();
        circleSingleLinkedList.addBoy(5);
        circleSingleLinkedList.countBoy(1,2,5);
    }
}

class CircleSingleLinkedList{
    private Boy first = new Boy(-1);

    public void addBoy(int nums){
        if(nums < 1){
            System.out.println("nums值不正确");
            return;
        }
        Boy curBoy = null;
        for(int i = 1;i <= nums ; i++){
            Boy boy = new Boy(i);

            if(i == 1){
                first = boy;
                first.setNext(first);
                curBoy = first;
            }else{
                curBoy.setNext(boy);
                boy.setNext(first);
                curBoy = boy;
            }
        }
    }

    public void showBoy(){
        if(first == null){
            System.out.println("链表为空");
            return;
        }

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

    public void countBoy(int startNo,int countNum,int nums){

        if(first == null || startNo < 1  || startNo > nums){
            System.out.println("参数输入有误，请重新输入");
            return;
        }
        //将helper指向环形链表的最后一个节点
        Boy helper = first;
        while(true){
            if(helper.getNext() == first){
                break;
            }
            helper = helper.getNext();
        }

        //将helper和startNo向后移到startNo处
        for(int j = 0; j< startNo - 1;j++){
            first= first.getNext();
            helper = helper.getNext();
        }
        //开始出圈
        while(true){
            if(helper == first){
                break;
            }
            for (int i = 0; i < countNum-1; i++) {
                first = first.getNext();
                helper = helper.getNext();
            }
            System.out.printf("小孩%d出圈\n",first.getNo());
            first = first.getNext();
            helper.setNext(first);
        }
        System.out.printf("最后留在圈中的小孩编号为%d\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;
    }
}

      三、测试结果

小孩2出圈
小孩4出圈
小孩1出圈
小孩5出圈
最后留在圈中的小孩编号为3