LeetCode - 19. Remove Nth Node From End of List

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* empty = new ListNode(-1);
        empty->next = head;
        ListNode* slow = empty, *fast = empty;
        for(int i=0;i<n;i++){
            fast = fast->next;
        }
        while(fast->next){
            slow = slow->next;
            fast = fast->next;
        }
        slow->next = slow->next->next;
        return empty->next; 
    }
};