LeetCode—— 删除链表的倒数第N个节点

题目地址：https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/

解题思路：题目要求一次遍历，设置双指针，通过第二个指针来判断是否第一个指针到达倒数第n个。

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode *p, *q;
        p = q = head;
        for (int i = 0; i < n ; i++)
            p = p->next;
        if(p==NULL)
            return head->next;
        while (p->next != NULL) {
            q = q->next;
            p = p->next;
        }
        q->next = q->next->next;
        return head;
    }
};