19. Remove Nth Node From End of List | LeetCode Solution
Given the head
of a linked list, remove the nth
node from the end of the list and return its head.
Example 1:

Input: head = [1,2,3,4,5], n = 2 Output: [1,2,3,5]
Example 2:
Input: head = [1], n = 1 Output: []
Example 3:
Input: head = [1,2], n = 1 Output: [1]
Constraints:
- The number of nodes in the list is
sz
. 1 <= sz <= 30
0 <= Node.val <= 100
1 <= n <= sz
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* removeNthFromEnd(ListNode* head, int n) {
if((n==1 && head==NULL) || (head->next==NULL && n==1))return NULL;
ListNode* fast=head;
ListNode* slow=head;
while(n--){
fast=fast->next;
}
if(fast==NULL)return head->next;
while(fast->next!=NULL){
fast=fast->next;
slow=slow->next;
}
slow->next=slow->next->next;
return head;
}
};
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