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【leetcode刷题笔记】Remove Nth Node From End of List

时间:2014-07-21 09:02:01      阅读:161      评论:0      收藏:0      [点我收藏+]

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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.


 

题解:快慢指针的思想,就像找到链表中点或者判断链表是否有环一样,是很经典的思想。

设置fast指针比slow指针多走n步,然后slow和fast一起前进,当fast指向null的时候,slow就指向从后往前数的第n个元素了。

但是要删除某个节点,最好的是知道它前面的节点,所以slow实际比fast慢n+1步。

代码如下:

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) {
 7  *         val = x;
 8  *         next = null;
 9  *     }
10  * }
11  */
12 public class Solution {
13     public ListNode removeNthFromEnd(ListNode head, int n) {
14         if(head == null)
15             return null;
16         
17         ListNode slow = new ListNode(0);
18         ListNode answer = slow;
19         slow.next = head;
20         ListNode fast = head;
21         for(int i = 0;i < n;i++){
22             if(fast == null)
23                 return null;
24             fast = fast.next;
25         }
26         while(fast != null){
27             slow = slow.next;
28             fast = fast.next;
29         }
30         
31         //delete what slow.next
32         slow.next = slow.next.next;
33         return answer.next;
34     }
35 }

【leetcode刷题笔记】Remove Nth Node From End of List,布布扣,bubuko.com

【leetcode刷题笔记】Remove Nth Node From End of List

标签:style   blog   color   strong   io   for   

原文地址:http://www.cnblogs.com/sunshineatnoon/p/3856453.html

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