class Solution { public: ListNode* removeNthFromEnd(ListNode* head, int n) { // 由于可能会删除链表头部，用哨兵节点简化代码 ListNode dummy{0, head}; auto left = &dummy; auto right = &dummy; while (n--) { right = right->next; // 右指针先向右走 n 步 } while (right->next) { left = left->next; right = right->next; // 左右指针一起走 } // 左指针的下一个节点就是倒数第 n 个节点 auto nxt = left->next; left->next = left->next->next; delete nxt; return dummy.next; } };