Java 环形单链表解决约瑟夫问题

环形单链表解决约瑟夫问题

package linkedlist;

public class Josephu<T> {
    private Node<T> head;
    private int size = 0;

    /**
     * 约瑟夫问题
     * 输入数据的总数直接从size中读取，可以不显示的指定
     * 删除数到的节点
     *
     * @param startNum 从第几个元素开始数
     * @param countNum 数几下
     */
    public void count(int startNum, int countNum) {
        if (startNum > size || startNum <= 0 || countNum <= 0) {
            System.out.printf("param is invalid");
            return;
        }

        // temp指向待删除元素的前一根元素，初始化为head的前一个元素
        Node<T> temp = head;
        for (int i = 0; i < size - 1; i++) {
            temp = temp.next;
        }

        // 头节点置位null，这样才可以删除头节点指向的元素
        head = null;

        //temp指向数数的起点的前一个元素
        for (int i = 0; i < startNum - 1; i++) {
            temp = temp.next;
        }

        // 计数器
        int skipCount = 0;

        // 总共会输出size个元素
        while (size > 0) {
            // 环形链表内循环数数，数到第countNum的元素删除
            for (int i = 0; i < countNum; i++) {
                if (skipCount + 1 == countNum) {
                    System.out.print(temp.next.item + " ");
                    skipCount = 0;
                    temp.next = temp.next.next;
                    size--;
                } else {
                    skipCount++;
                    temp = temp.next;
                }
            }
        }

        System.out.println();
    }

    public int getSize() {
        return size;
    }

    public void print() {
        Node<T> temp = head;
        for (int i = 0; i < size && null != temp; i++) {
            System.out.printf(temp.item + " ");
            temp = temp.next;
        }
        System.out.println();
    }

    public void add(T data) {
        Node<T> newData = new Node<>(data, null);
        Node<T> temp = head;

        for (int i = 0; i < size - 1; i++) {
            temp = temp.next;
        }

        // 链表为空处理
        if (null == temp) {
            head = newData;
            newData.next = head;
        } else {
            // 插入数据到链表的尾部
            temp.next = newData;
            newData.next = head;
        }
        size++;
    }

    private static class Node<T> {
        T item;
        Node<T> next;

        public Node(T item, Node<T> next) {
            this.item = item;
            this.next = next;
        }
    }
}