/*
* @lc app=leetcode id=19 lang=cpp
*
* [19] Remove Nth Node From End of List
*
* https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/
*
* algorithms
* Medium (34.54%)
* Likes: 2090
* Dislikes: 158
* Total Accepted: 441.2K
* Total Submissions: 1.3M
* Testcase Example: '[1,2,3,4,5]\n2'
*
* Given a linked list, remove the n-th node from the end of list and return
* its head.
*
* 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.
*
* Follow up:
*
* Could you 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) {
auto first = head, sec = head;
for (int i = 0; i < n; ++i) first = first->next;
if (first == nullptr) return head->next;
while (first->next != nullptr) {
first = first->next;
sec = sec->next;
}
sec->next = sec->next->next;
return head;
}
};