數據結構學習（四）：約瑟夫環

一、定義節點

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 +
                '}';
    }
}

二、創建一個first節點，當前沒有編號

private  Boy first = new Boy(-1);

三、添加節點，構建成一個環形的鏈表

public void addBoy(int nums) {
        if(nums < 1) {
            System.out.println("num incorrect");
            return;
        }

        //輔助指針，幫助構建環形鏈表
        Boy curBoy = null;

        //使用for構建環形鏈表
        for (int i = 1; i <= nums; i++) {
            //按照編號，構建小孩節點
            Boy boy = new Boy(i);
            //如果是第一個小孩
            if(i == 1) {
                first = boy;
                //構成環
                first.setNext(first);
                //讓curBoy指向第一個小孩
                curBoy = first;
            }else {
                curBoy.setNext(boy);
                //形成環
                boy.setNext(first);
                //往後移動
                curBoy = boy;
            }
        }
    }

四、遍歷

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

        //因爲first不能動，所以仍然使用一個輔助指針完成遍歷
        Boy curBoy = first;
        while (true) {
            System.out.println("num: " + curBoy.getNo());
            if(curBoy.getNext() == first) {
                break;
            }
            curBoy = curBoy.getNext();
        }
    }

五、根據用戶的輸入，計算節點出圈的順序

startNo:從第幾個節點開始數
countNum:數幾下
nums:最初有幾個節點在圈中

public void countBoy(int startNo, int countNum, int nums) {
        if(first == null || startNo < 1 || startNo > nums) {
            System.out.println("input incorrect");
            return;
        }

        //創建輔助變量
        Boy helper = first;
        //讓helper指向最後一個節點
        while (true) {
            if(helper.getNext() == first) {
                break;
            }
            helper = helper.getNext();
        }

        //報數前，先讓first和helper同時移動startNo-1次
        for (int i = 0; i < startNo - 1; i++) {
            first = first.getNext();
            helper = helper.getNext();
        }

        //報數時，讓first和helper同時移動countNum-1次,然後出圈
        while (true) {
            //圈中只有一個節點
            if(helper == first) {
                break;
            }
            //讓first和helper同時移動countNum - 1
            for (int i = 0; i < countNum - 1; i++) {
                first = first.getNext();
                helper = helper.getNext();
            }

            //這時first指向的節點，就是要出圈的小小孩節點
            System.out.println("go out " + first.getNo());
            first = first.getNext();
            helper.setNext(first);
        }
        System.out.println("最後留在圈中的編號：" + first.getNo());

    }

六、測試

public static void main(String[] args) {
        CircleSingleLinkedList circleSingleLinkedList = new CircleSingleLinkedList();
        circleSingleLinkedList.addBoy(5);
        circleSingleLinkedList.showBoy();

        circleSingleLinkedList.countBoy(1,2,5);
    }