Remove Nth Node From End of List

 

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Question Solution 

 

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.

 

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SOLUTION 1:

1.使用快慢指针，快指针先行移动N步。用慢指针指向要移除的Node的前一个Node.

2. 使用dummy node作为head的前缀节点，这样就算是删除head也能轻松handle啦！

主页君是不是很聪明呀？ :)

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         // 001715         ListNode dummy = new ListNode(0);16         dummy.next = head;17         18         ListNode slow = dummy;19         ListNode fast = dummy;20         21         // move fast N more than slow.22         while (n > 0) {23             fast = fast.next;24             // Bug 1: FORGET THE N--;25             n--;26         }27         28         while (fast.next != null) {29             fast = fast.next;30             slow = slow.next;31         }32         33         // Slow is the pre node of the node which we want to delete.34         slow.next = slow.next.next;35         36         return dummy.next;37     }38 }

 

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