圆圈中最后剩下的数字（Java实现）

public class E62LastRemainNumber {
    //圆圈中最后剩下的数字

    /*解法一：构造环形链表*/
    static class ListNode<T> {
        //环形链表节点
        T value;
        ListNode<T> nextNode;

        ListNode(T value) {
            this.value = value;
        }
    }

    static class AnnularLinkedList<T> {
        //链表结构
        private int size;
        private ListNode<T> first;
        private ListNode<T> last;

        public int size() {
            return size;
        }

        public ListNode<T> getFirstNode() {
            if (size == 0)
                throw new IllegalArgumentException("Empty!");
            return first;
        }

        public ListNode<T> getLastNode() {
            if (size == 0)
                throw new IllegalArgumentException("Empty!");
            return last;
        }

        public void add(T element) {
            ListNode<T> node = new ListNode<>(element);
            if (size == 0) {
                first = node;
                last = node;
            } else {
                last.nextNode = node;
                last = node;
            }
            size++;
        }

        public void remove(ListNode<T> listNode) {
            if (size == 0)
                throw new IllegalArgumentException("Empty! No element to remove!");
            ListNode<T> pre = first;
            ListNode<T> node = pre;
            while (node != null && node != listNode) {
                pre = node;
                node = node.nextNode;
            }
            if (node == null)
                throw new IllegalArgumentException("No Such Element!");
            else if (size == 1) {
                first = null;
                last = null;
            }
            else if (pre == node){
                first = node.nextNode;
            }
            else{
                pre.nextNode = node.nextNode;
            }
            size--;
        }
    }

    public static int getNumber1(int n, int m) {
        if (n < 1 || m < 1)
            return -1;
        AnnularLinkedList<Integer> list = new AnnularLinkedList<>();
        for (int i = 0; i < n; i++)
            list.add(i);
        ListNode<Integer> current = list.getFirstNode();
        while (list.size() > 1) {
            for (int i = 1; i < m; i++) {
                current = current.nextNode;
                if (current == null)
                    current = list.getFirstNode();
            }
            ListNode<Integer> next = current.nextNode;
            if (next == null)
                next = list.getFirstNode();
            list.remove(current);
            current = next;
        }
        return current.value;
    }

    /*解法二：推导出数学公式*/
    public static int getNumber2(int n, int m){
        if (n < 1 || m < 1)
            return -1;
        int result = 0;
        for (int i = 2; i <= n; i++){
            result = (result + m) % i;
        }
        return result;
    }

    //测试用例
    public static void main(String[] args) {
        System.out.println(E62LastRemainNumber.getNumber1(4000, 997)); //1027
        System.out.println(E62LastRemainNumber.getNumber2(4000, 997)); //1027
    }
}