學習筆記-約瑟夫問題之環形鏈表

約瑟夫問題java代碼

curBoy爲輔助節點

我測試的是5個人的，最終答案是24153。

public class Josepfu {
    public static void main(String[] args) {
        CircleSingleLinkedList cs = new CircleSingleLinkedList();
        cs.addBoy(5);
        cs.list();
        //測試小孩出圈是否成功
        cs.countBoy(1, 2, 5);
    }
}

class CircleSingleLinkedList{
    private Boy first = null;

    public void addBoy(Integer nums){
        if (nums < 1){
            System.out.println("編號不正確!");
            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;
            }
        }
    }
    //遍歷當前環形鏈表
    public void list(){
        //判斷是否爲空
        if (first == null){
            System.out.println("鏈表爲空");
            return;
        }
        //因爲first不能動，因此我們仍需要一個輔助指針
        Boy curBoy = first;
        while (true){
            System.out.printf("小孩的編號是%d\n", curBoy.getNo());
            if (curBoy.getNext() == first){
                break;
            }
            curBoy = curBoy.getNext();
        }
    }

    /**
     *
     * @param startNo 表示從第幾個小孩開始數數
     * @param countNums 表示數幾下
     * @param nums 表示最初有多少小孩在圈中
     */
    public void countBoy(int startNo, int countNums, int nums){
        if (first == null || startNo < 1 || startNo > nums){
            System.out.println("參數輸入有誤,請重新輸入!");
            return;
        }
        Boy helper = first;
        while (true){
            if (helper.getNext() == first){
                break;
            }
            helper = helper.getNext();
        }
        //小孩報數前先讓first和helper移動k - 1次
        for (int j = 0; j < startNo - 1; j++){
            first = first.getNext();
            helper = helper.getNext();
        }
        //當小孩報數時，helper和first同時移動m-1次
        while (true){
            //說明圈中只有一個節點
            if (helper == first){
                break;
            }

            //讓first和helper同時移動countNum-1
            for (int j = 0; j < countNums - 1; j++){
                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("最後留在圈中的小孩是%d", first.getNo());
    }

}

class Boy{
    private Integer no;
    private Boy next;

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

    public Integer getNo() {
        return no;
    }

    public Boy getNext() {
        return next;
    }

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

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

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

運行結果