删除链表的倒数n个节点

#include<iostream>
#include<vector>
using namespace std;
 struct ListNode {
     int val;
     ListNode *next;
     ListNode(int x) : val(x), next(NULL) {}
  };
 
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) 
    {
        ListNode* p=head;
        ListNode* q=head->next;
        int num = 0;//计算p和q之间存在几个节点
        while (q)
        {
            if (num <n)
            {
                q = q->next;
                num++;
            }
            else 
            {
                q = q->next;
                p = p->next;
            }
        }
        //删除p后面的一个顶点
        ListNode* temp = p->next;
        p->next = p->next->next;
        delete temp;
        return head;
    }
};
//测试-----------------
void input(ListNode* l)
{
    int num;
    while (1)
    {
        cin >> num;
        if (num == -1)
            return;
        ListNode* newNode = new ListNode(num);
        newNode->next = l->next;
        l->next = newNode;
    }

}
void display(ListNode* l)
{
    if (l== NULL)
    {
        return;
    }
    cout << l->val;
    display(l->next);
}
void test()
{
    ListNode* l = new ListNode(0);
    input(l);
    Solution s;
   l=s.removeNthFromEnd(l, 2);
    cout << "链表打印：" << endl;
    display(l->next);
    cout << endl;
}
int main()
{
    test();
    system("pause");
    return 0;
}