约瑟夫问题

约瑟夫问题：N个人围成一圈，从约定编号为K的人开始报数，第M个将被杀掉，依次类推，最后剩下一个，其余人都将被杀掉。

直接上图展示，初始化状态： 假设n=6，总共有6个人，k=1,从第一个人开始报数，m=5,每次数五个。

package linkedlist;

public class josepfu {

    public static void main(String[] args) {
//构建环形链表
        CirclesingleLinkedList circlesingleLinkedList = new CirclesingleLinkedList();
        circlesingleLinkedList.addBoy(5);
        circlesingleLinkedList.showBoy();
        circlesingleLinkedList.countBoy(1, 2, 5);
    }

}

//创建环形单向链表
class CirclesingleLinkedList {
    private Boy first = new Boy(-1);

    public void addBoy(int nums) {
        if (nums < 1) {
            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;
            }
        }
    }

    // 遍历当前环形链表
    public void showBoy() {
        if (first == null) {
            System.out.println("没有任何小孩");
            return;
        }
        Boy curBoy = first;
        while (true) {
            System.out.println("小孩的编号" + curBoy.getNo());
            if (curBoy.getNext() == first) {
                break;
            }
            curBoy = curBoy.getNext();

        }
    }

    // 根据用户的输入，计算小孩出圈的顺序
    /**
     * 
     * @param startNo表示从第几个小孩开始数数
     * @param counntNum表示数几下
     * @param nums表示最初有多少小孩在圈中
     */
    public void countBoy(int startNo, int countNum, int nums) {
        // 先对数据校验
        if (first == null || startNo < 1 || startNo > nums) {
            System.out.println("参数有误");
        }
        Boy helper = first;
        // helper指向环形链表的最后节点
        while (true) {
            if (helper.getNext() == first) {
                break;
            }
            helper = helper.getNext();
        }
        // 小孩报数前，先让first和helper移动k-1次
        for (int j = 0; j < startNo - 1; j++) {
            first = first.getNext();
            helper = helper.getNext();
        }
        // 让first和helper指针同时移动m-1次，然后出圈
        while (true) {
            if (helper == first) {// 圈中只有一个
                break;

            }
            // 让first和helper指针同时移动countNum-1
            for (int j = 0; j < countNum - 1; j++) {
                first = first.getNext();
                helper = helper.getNext();
            }
            // 这时first指向的节点，就是要出圈的小孩节点
            System.out.println("小孩" + first.getNo() + "出圈");
            first = first.getNext();
            helper.setNext(first);
        }
        System.out.println("留在圈中的小孩编号" + first.getNo());
    }

}

class Boy {
    private int no;
    private Boy next;

    public Boy(int no) {
        super();
        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;
    };

}