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/**

* Practiced on 12/31/2012

*

* 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.

*

* =======================================

* The following function considers also invalid n.

*/

package com.congli.leetcode;

public class RemoveNthNodeFromList {

public ListNode removeNthFromEnd(ListNode head, int n)

{

if(n <= 0) return head;

int i = 1;

ListNode runner = head;

while(runner != null && i < n)

{

runner = runner.next;

++i;

}

if(runner == null) return head; // n is larger than the length of the list

if(runner.next == null) // n equals the length of the list

{

head = head.next;

return head;

}

ListNode first = head;

while(runner.next.next != null)

{

first = first.next;

runner = runner.next;

}

first.next = first.next.next;

return head;

}

}