力扣中的算法问题，这句是什么意思有什么意义

Question

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* dummy = new ListNode(0, head);
        ListNode* first = head;
        ListNode* second = dummy;
        for (int i = 0; i < n; ++i) {
            first = first->next;
        }
        while (first) {
            first = first->next;
            second = second->next;
        }
/********在这里在来这里************/
        second->next = second->next->next;  //这里这里这里
/*******上面这句********************/      
  ListNode* ans = dummy->next;
        delete dummy;
        return ans;
    }
};

作者：LeetCode-Solution
链接：https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/solution/shan-chu-lian-biao-de-dao-shu-di-nge-jie-dian-b-61/
来源：力扣（LeetCode）
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Answer 1