19. Remove Nth Node From End of List

ListNode* removeNthFromEnd(ListNode* head, int n) {
ListNode* first = head;
ListNode* second = head;
int i = 0;
while (second) {
i++;
second = second->next;
}
int j= 0;
if(i==n) return head->next;
while (j < i-n -1) {
first = first->next;
j++;
}
first->next = first->next->next;
return head;
}