LeetCode Online Judge 题目C# 练习 - Remove Nth Node From End of List

Given a linked list, remove the nth 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.

 1         public static LinkedListNode RemoveNthNodeFromEndofList(LinkedListNode head, int n)
 2         {
 3 
 4             LinkedListNode p = head;
 5             LinkedListNode q = head;
 6 
 7             for (int i = 0; i < n; i++)
 8             {
 9                 //if p == null mean the node to be remove is head node
10                 if (p == null)
11                     return head.Next;
12                 p = p.Next;
13             }
14 
15             while (p != null)
16             {
17                 p = p.Next;
18                 q = q.Next;
19             }
20 
21             //remove the q.next;
22             q.Next = q.Next.Next;
23 
24             return head;
25         }

代码分析：

　　做两指针，p， q（q将指向要remove的前一个node）。p先走 n + 1 步，如果p 走到尾了 （p == null)， 那证明所要移除的是head node， 那直接返回head.next搞定。然后p， q一起往前走，让p走到底， 那么这时候q.next就是要移除的node。 q.next = q.next.next 移除之。