[数据结构与算法]约瑟夫环问题（Java） 2021.12.23

约瑟夫环问题全部Java代码如下：

package DataStructures.linkedList;

public class Josepfu {

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

//创建一个单向循环链表
class CircleSingleLinkedList{
    private Boy first = null;

    public void addBoy(int nums){
        if( nums < 2 ){
            System.out.println("nums的值不正确！");
            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;
            }
        }
    }

    //遍历当前链表
    public void showBoy(){
        if( first == null ){
            System.out.println("没有小孩！");
            return;
        }
        Boy curBoy = first;
        while( true ){
            System.out.printf("小孩编号：%d\n",curBoy.getNo());
            if(curBoy.getNext() == first){
                break;
            }
            curBoy = curBoy.getNext();
        }
    }

    //根据用户输入，计算出小孩出圈的顺序

    /**
     *
     * @param startNo   表示从第几个小孩开始数数
     * @param countNum   表示数几下
     * @param nums   表示最开始有多少小孩在圈中
     */
    public void countBoy(int startNo, int countNum, int nums){
        if( first == null || startNo < 1 || startNo > nums ){
            System.out.println("输入数据有误，请重新输入...");
            return;
        }
        Boy helper = first;
        while(true){
            if( helper.getNext() == first ){
                break;
            }
            helper = helper.getNext();
        }

        //小孩报数前，先让first和helper移动(startNo - 1)次
        for (int i = 0; i < startNo - 1; i++) {
            first = first.getNext();
            helper = helper.getNext();
        }

        //开始报数出圈
        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());
            helper.setNext(first.getNext());
            first = first.getNext();
        }
        System.out.printf("最后留在圈中的小孩为%d\n",first.getNo());
    }
}

//创建一个Boy类，表示一个节点
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;
    }
}

执行结果如图：

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