19.1.29 [LeetCode 19] Remove Nth Node From End of List

Given a linked list, remove the n-th node from the end of list and return its head.

Example:

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:

Given n will always be valid.

Follow up:

Could you do this in one pass?

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode hh(0);
        hh.next = head;
        ListNode*hhead = &hh;
        ListNode*first = hhead, *second = hhead->next->next;
        int count = 0;
        while (head) {
            count++;
            if (count >= n+1) {
                first = first->next;
                second = second->next;
            }
            if (head->next == NULL) {
                first->next = second;
                break;
            }
            head = head->next;
        }
        return hhead->next;
    }
};