19.cpp

#include <bits/stdc++.h>
#include "ListNode.cpp"
using namespace std;

class Solution {
public:
    Solution() {
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout.tie(0);
    }
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        ListNode* first = dummy;
        ListNode* second = dummy;
        for (int i = 1; i <= n + 1; i++) {
            first = first->next;
        }
        while (first != nullptr) {
            first = first->next;
            second = second->next;
        }
        second->next = second->next->next;
        return dummy->next;
    }
};