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.

Solution:

Tips:

two pointers, one pointer goes first, and then the other goes after the first pointer's N steps.

Java Code:

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; } * } */public class Solution {    public ListNode removeNthFromEnd(ListNode head, int n) {        if (head == null) {            return head;        }                ListNode tmpNode = head;        ListNode tmpNodeNth = head;        while ((n--) > 0) {            tmpNodeNth = tmpNodeNth.next;        }        if (tmpNodeNth == null) {            return head.next;        }                tmpNodeNth = tmpNodeNth.next;        while (tmpNodeNth != null) {            tmpNodeNth = tmpNodeNth.next;            tmpNode = tmpNode.next;        }        tmpNode.next = tmpNode.next.next;                return head;    }}