/**

 * Definition for singly-linked list.

 * struct ListNode {

 *     int val;

 *     ListNode *next;

 *     ListNode() : val(0), next(nullptr) {}

 *     ListNode(int x) : val(x), next(nullptr) {}

 *     ListNode(int x, ListNode *next) : val(x), next(next) {}

 * };

 */

class Solution {

public:

    ListNode* removeNthFromEnd(ListNode* head, int n) {

        ListNode *p = head, *q = head, *l = head;

        while(p->next != NULL)

        {

            p = p->next;

            n--;

            if(n <= 0)

            {

                l = q;

                q = q->next;

            }

        }

        if(q == head)

        {

            head = q->next;

        }

        else

        {

            l->next = q->next;

        }

        delete q;

        return head;

    }

};