旋转链表

61. 旋转链表

public ListNode rotateRight(ListNode head, int k) {
        if (head == null || k == 0) {
            return head;
        }
        ListNode tmp = head;
        int len = 0;
        while (tmp != null) {
            tmp = tmp.next;
            len++;
        }
        k = k % len;
        if (k == 0) {
            return head;
        }
        //快慢指针
        tmp = head;
        ListNode node = head;
        while (k > 0) {
            k--;
            tmp = tmp.next;
        }
        while (tmp.next != null) {
            head = head.next;
            tmp = tmp.next;
        }
        //记录next的位置
        ListNode res = head.next;
        //断开连接
        head.next = null;
        //后一段的末尾指向前一段的开头
        tmp.next = node;
        return res;
    }