19. 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.

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* removeNthFromEnd(ListNode* head, int n) {        ListNode* result=new ListNode(0);result->next=head;int length=0;ListNode* p=result;while(p->next){length++;p=p->next;}p=result;if(length==0||length<n) return result->next;int point=length-n+1;int i=1;while(p->next){if(i==point){p->next=p->next->next;break;}p=p->next;i++;}return result->next;    }};