LeetCode OJ:Remove Nth Node From End of List

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 *nh=new ListNode(0);
nh->next=head;
ListNode *p=nh,*q=head,*r=nh;

while(q){
if(--n<=0){
r=p;
p=p->next;
}
q=q->next;
}
r->next=p->next;
delete[] p;
return nh->next;
}
};