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.

For 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.

Try to do this in one pass.

代码如下：

/**
 * 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 (head == NULL)
				return head;
			ListNode *p=head, *q = head;
			for (int i =0; i<n; i++)
			{
				if (p)
				{
					p = p->next;
				}else
					return head;
			}
			if (p == NULL)
			{
				head = head->next;
				return head;
			}
			while(p->next != NULL){
				p = p->next;
				q = q->next;
			}
			q->next = q->next->next;
			return head;

    }
};