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19. Remove Nth Node From End of List

Medium

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

Follow up: Could you do this in one pass?

Solution

using LeetCodeNet.Com_github_leetcode;

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution {
    private int n;

    public ListNode RemoveNthFromEnd(ListNode head, int n) {
        this.n = n;
        ListNode node = new ListNode(0, head);
        RemoveNth(node);
        return node.next;
    }

    private void RemoveNth(ListNode node) {
        if (node.next == null) {
            return;
        }
        RemoveNth(node.next);
        this.n--;

        if (this.n == 0) {
            node.next = node.next.next;
        }
    }
}

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