> For the complete documentation index, see [llms.txt](https://protegejj.gitbook.io/oj-practices/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://protegejj.gitbook.io/oj-practices/chapter1/linked-list/19-removenth-node-from-end-of-list.md).

# 19     Remove Nth Node From End of List

## 19. [Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/)

## 1. Question

Given a linked list, remove thenthnode 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.

## 2. Implementation

```java
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;

        ListNode fast = dummy, slow = dummy;

        for (int i = 1; i <= n + 1; i++) {
            fast = fast.next;
        }

        while (fast != null) {
            fast = fast.next;
            slow = slow.next;
        }

        slow.next = slow.next.next;
        return dummy.next;
    }
}
```

## 3. Time & Space Complexity

时间复杂度O(n), 空间复杂度O(1)