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) {
      //  if(n==0) return head;
        int count = 0;//总的链表长度
        ListNode *Head = (ListNode *)malloc(sizeof(ListNode));
        Head->next = head;//为链表加一个头结点
        ListNode *tail = head;
        while(tail) {
            count++;
            tail = tail->next;
        }
        //if(count<n) return NULL;
        int num = count-n;
        tail = Head;
        while(num--){//找到要删除节点的前一个节点的位置
            tail = tail->next;
        }
        tail->next = tail->next->next;//删除节点
        return Head->next;
    }
};